"Yeah, he's flying out tonight. I don't know, a few days at least." said Lydia. She was on the phone to her best friend when she felt a tug on her skirt. Without a second's pause the 34 year old golden retriever knelt in front of the couch, resting her front on the cushions, her back arched and her inviting rear thrust up.
"Listen, would you like to come over?" she asked, as a small pair of hands flipped her skirt up and slid her panties down her round ass, and Lydia accommodated by lifting her tail. 
"We could have a few drinks and watch a few movies..." she continued, her voice giving no indication that the speaker's rump was being fondled as somebody positioned themselves behind her. 
"Yeah, he drove to the office a few minutes ago, some last-minute thing". She stifled a moan as her mound was briefly probed before being unceremoniously penetrated.  Lydia continued her conversation, her voice giving no indication that she was being gently rutted.
"Of course you can spend the night! Hold on a sec..." Lydia said, covering the microphone with her thumb and turning around.
"Tyler, honey, we've been over this. You have to wear a condom if you want mommy's pussy." She admonished her twelve year old son, who was at very moment humping away at her cunny.
"Aww..." Tyler groaned, but knew his mother wouldn't budge on this point. Ever since he started to shoot his goo, his mother had been adamant about those stupid rubbers. Still, she did give him an alternative, and Tyler didn't feel like going upstairs just to get a condom. He pulled out of his mother's muff, his young stiffy already covered in their combined juices.
"OK, come over at about nine?" Lydia continued, a slight huff getting past her lips as her son shoved himself under her tail none too gently, annoyed that she made him switch.
"Great, see you then. Bye!" she sighed as she hung up. Now she could turn her attention to the boy currently pistoning in and out of her pucker.
"Tyler - ahh - did you lock the door?" she asked.
"Yes mom." Tyler said, rolling his eyes. They had to go through this every time.
"And did you draw the curtains?" she asked, wincing a bit as her son picked up his tempo.
"Yes mom!"
"Good boy. Now go ahead and show mommy how much you love her!" she said, resting her head on the couch as her son pumped her ass with practiced strokes, his knot still deflated and slipping in and out of her with every thrust.
Lydia knew how shocked other people, including her husband, would be if they found out about her relationship with her son, which is why she drilled him so much about privacy and secrecy. She, on the other hand, saw nothing wrong with her relationship with Tyler. Her husband had managed to talk her into only having one child, and since Tyler would remain her one and only she was determined to deny her baby nothing. 
She fell in love with the pup the moment they handed him to her in the hospital, when his little muzzle unerringly sought out her nipple and he started to nurse. She never really stopped breastfeeding him. When her milk production dropped off they still had their secret little nursing sessions, the two lying naked together in bed as Tyler nuzzled her breasts. He could still coax a bit of milk out of them, but it had become more about cuddling with his mother. When he was ten he started getting stiff when they did it, and it wasn't long before the cuddling got a bit... out of hand. He was lying on top of Lydia, who had tickled him a bit, causing him to slip down to escape her fingers. As he crawled back atop his mother his tapered tip caught against her labia and Lydia froze, realizing their little bonding sessions were on the verge of becoming something more. Still, she wouldn't deny her baby any sort of affection. She kissed the top of his head, letting him know she loved him, and he slid inside her with the cutest little moan she ever heard! She held him close, telling him how much she loved him as he gave a few sharp, shallow thrusts before his little knot lodged inside his mother and his young cock twitched. He was still too young to fill his mother's pussy, but Lydia's heart melted as she realized her boy had just given her his virginity.
Afterwards she had the sex talk with him, which she knew was normal. She also had the sworn-to-secrecy talk with him which she realized wasn't normal, but she didn't care. Her little treasure deserved better than 'normal'. Since then their nursing sessions got more interesting, as mother and son explored each other's bodies and Lydia showed her son all kinds of ways to have sex. It was almost a year ago, after giving her son a quick blow job before sending him to school, that Lydia noticed the stuff she was licking off her baby's cock was looking a bit milky-white. It was then that the unpopular condom rule was instated.  She felt a bit bad for making him wrap up, and considered going on the pill, but she held a very strong view on unnecessary pharmaceuticals.
Still, as her current situation proved, Tyler had grown to enjoy anal. He was always more vigorous when mounting her rump, and Lydia suspected he hoped his mother would get tired of the rough treatment and beg him to start stuffing her pussy bareback again. If so, it was wishful thinking on his part. Although she could only take her husband beneath her tail if he went slow, she found she enjoyed her son's four inch cock well enough even when he gave it to her as hard as he could. Still, she gave him a few grunts and whines now and then, to make him feel like a big man.
He was gripping the base of her tail now, the possessive gesture making Lydia hornier. It wasn't long before his knot inflated enough that he couldn't pull it out and he was limited to very shallow thrusts, the bulb tugging on his mother's ring every time he pulled back. Lydia quickly reached back with one hand, her fingers attacking her clit as she felt her son's member inflate inside her. She rubbed herself as her son's hips kept nudging into her curvy ass and making her cheeks jiggle. It wasn't long before he dove himself in as far as he could, his fingers digging into his mother's ass as his cock throbbed and shot his load inside her. Hearing his adorable groans and feeling the warmth of his seed start to spread through her, Lydia let herself go and came all over her hand, her sphincter twitching rhythmically around her son's cock. He lay on top of her and they shared a tender moment while they waited for Tyler's knot to shrink, Tyler nuzzling the back of his mother's neck as she cooed to him. After a few minutes, Tyler pulled back and with a slight 'pop' slipped his knot out of his mother's ass.
                "What do you say, honey?" she asked as she felt the rest of her son's length withdraw from her rear.
                "I love you, mommy." Tyler replied, still in a post-orgasmic daze.
"Mommy loves you too sweetie. Now go upstairs and clean up before daddy comes back." Lydia replied. Unlocking a small chest under the end table she rummaged around until she found whet she was looking for. She picked up the tiny butt-plug, just big enough to stay wedged inside her, and slid it under her tail. She'd have a proper shower a little later and didn't feel like cleaning up before that. Plus, she did enjoy the sensation of her baby's seed sloshing inside her, as long as there was no danger of another little baby coming along because of it.
*******
Lydia had just seen Robert off when a few minutes later Robyn pulled up. Not that she was worried about them crossing paths. Robyn had been Lydia's best friend ever since they were roommates in college, and her husband knew they had a special relationship. Lydia had told him all about it way back before they got married, and he'd always been very understanding about it. He traveled a lot, and Lydia supposed he was glad that she had the vixen to keep her company, rather than another man. For her part, Lydia made sure to send him a few pics of them together when he was away, figuring that if she gave him something to jack off to he'd be less tempted to cheat on her.
The two women hugged in the doorway, both eager to spend some quality time together, especially after Tyler went to bed. 
"Aunt Robyn!" the pup cried trotting over to the vixen who'd babysat him whenever his parents went out on a date. Robyn leaned over to hug the boy, noting as always how physically affectionate he was. His hands always seemed quite confident, and being cute to boot, Robyn was sure Tyler would be a real lady-killer in a few years. And even though he was getting bigger every time she came over, she still viewed him as an adorable little puppy.
They went to the living room and sat together for a while, chatting and catching up, until Lydia announced it was time for Tyler's bedtime. Tyler tried to talk her into letting him stay up more, and even though she often gave in to him, Lydia insisted he needed his rest since tomorrow was a school day. In truth, she was eager for a little alone time with Robyn, and had noticed the vixen was also squirming a bit. She tucked Tyler into bed and gave him a kiss. She usually gave him either a blowjob, or pawed him off to help him get to sleep, but she explained it would be rude to let their guest wait all alone, and promised to make it up for him in the morning.
Once the pup was in bed, the women turned the lights down, put the movie on and got comfortable with a bottle of wine. Fifteen minutes later the movie was being ignored as the two women kissed, hands roaming each other's' bodies. Their quality time was interrupted by the chirping of Lydia's phone. She was just about to send it to voicemail when she noticed it was Robert calling.
"Hi honey, what's the matter? Oh damn, yes it's here. OK, I'll drive right over." She said, hanging up.
"Was that Robert?"
"Yeah, he forgot his briefcase and he can't leave without it. He'll be able to catch another flight, but he needs me to bring it over to him right away." She said, getting her car keys and jacket. "Listen Robyn, I'm terribly sorry about this, but do you mind waiting for me? I'll be back in about an hour, two at the most."
"Don't worry Lydia, it's fine. You do what you have to do, and when you come back we'll pick up where we left off."
"Thanks hon! I promise I'll make it up to you when I get back." She said, giving Robyn a deep kiss before grabbing the briefcase and going out the door.
Robyn got comfortable on the couch and settled in for the wait. She hit play, figuring she'd at least watch the movie, but about half an hour later she realized she'd finished the bottle before she finished the film. She switched it off and decided to go the bedroom and get ready for Lydia. She got out of her clothes and admired herself for a while in the full length mirror. The black bra and panties she was wearing stuck out against the white fur that ran from her chin to her crotch as she struk a few sexy poses. She never had kids so she still had a lithe figure, although she sometimes envied Lydia for the way pregnancy had filled her out.
"Oh well, I suppose you have to live with looking almost the same as you did in college." She told her reflection in mock despair. 
She thought about what she would do once that sexy bitch got back, and considered doing a strip-tease for her. While she toyed with the idea, she got horny and realizes neither of them would be in the mood for teasing. With that in mind, she got naked, and after a few more appreciative glances got under the sheets to wait for her friend. Once she got comfy she realized she'd gotten tipsier than she thought, and her eyelids were getting a bit heavy.
"Jus' a quick power nap... gonna give it to Lydia when she gets back..." she murmured as she curled up and drifted off to sleep.
*******
Tyler wasn't asleep for very long before he had a nightmare and woke up. Normally, whenever he had a bad dream he would go and get his mommy. After she woke up she would come back to his bed with him, so daddy could get his sleep. Once there she would let him mount her and after he came he would drift off to sleep, usually with his knot still inside his mother.
He went to his parent's bedroom, noticing the lights were still on but dimmed and someone was in bed. Walking over he realized it wasn't his mother, but Robyn. Realizing it was the middle of the night and his mother wasn't there for some reason definitely didn't make the pup feel any better, and he climbed into bed with the sleeping vixen, to calm himself down the only way he knew how...
*******
Robyn on the other hand was having a very nice dream indeed. She dreamt that Lydia had returned and was in bed with her. She was sighing contently as her best friend and lover fondled her breasts, her expert fingers pumping in and out of the vixen's honeypot. Slowly waking up, she realized the sensations were all too real and smiled, figuring Lydia had caught her dozing and was giving her a very nice wake-up call. Still curled up, she looked behind her and was so shocked by what she saw she almost screamed. Little Tyler was spooning up against her, his arms wrapped around her bare chest, his eyes screwed shut as he... as he fucked her!
"Tyler! Wh-what are you doing!?" she asked, still unable to believe what was happening.
"I had a bad dream and mommy wasn't here. I was scared so..." the pup trailed off, his hips still bucking against the vixen's behind.
Robyn couldn't believe what she was hearing. Did this boy just admit to having sex with his own mother while he was... raping her? She realized that's what was happening, that she should stop this, push the boy off her, but looking back into his eyes she didn't have the heart to do it. Tyler did seem upset, and she did really love the pup to bits. She supposed she could just let him finish, and then they could pretend it never happened.
"It's okay Tyler. Just... do what you need to do..." she whispered, feeling the kid pick up his pace. His knot was making wet squelching sounds as it slipped in and out of her wet pussy and she buried her muzzle into the pillow, realizing the boy had gotten her quite wet while she was asleep. She was horny and couldn't deny it felt nice having his shaft piston past her lips, but couldn't get over at how wrong it felt. This was her little Tyler, her best friend's twelve year old son, who she'd known since before he could walk. And now he was huffing into the back of her neck as his hips slapped against her rear.
What was also disturbing was the boy's skill. As he humped her at a steady pace, giving no signs of tiring, his hands seemed practiced as they fondled her breasts, brushing lightly over her stiff nipples as they did. She wondered how long this has been going on, just how often Lydia had sex with her own son? Try as she might, she couldn't imagine her friend as a bad mother. Tyler was the center of her world and she had a wonderful family. Was this how she did it? My God, what if he got her...
That train of thought brought a whole different concern to her attention.
"Tyler honey... you can't - ahh - finish inside. Just... pull out when you're close, okay sweetie?" Robyn couldn't believe the words, or the sounds, coming out of her mouth as she asked the twelve year old boy mounting her not to cum inside her. She wasn't even sure he was old enough to get her pregnant, but she was sure she didn't want to risk it. After he finishes they'll clean up, she'll put him back to bed and they'll never speak of this again. As long as he finishes before Lydia gets back...
With a start, Robyn realized she had no idea how long she'd been asleep. Lydia could be home any second, and Robyn realized that if she didn't want to get caught she'd have to get this over with as soon as possible. She tightened her muscles to try and stimulate Tyler a bit more. It seemed to do the trick, but it was stimulating both of them, and Robyn realized that the boy might actually get her off. A short while later his thrusts were getting shallower and he started grunting slightly.
"Sweetie, are you close?"
"U-huh..." the pup mumbled into her hear.
"You have to pull out honey... please... you can't finish inside." She pleaded, hoping the boy was listening.
She was relieved when she felt him slip his cock out of her and hung her head in embarrassment as she realized the kid she babysat for was about to paint her rump. But instead of a few spurts on her backside, the vixen felt her tail lifted slightly farther up a second before something wet and pointed pressed against her pucker. Before she could utter a word, Tyler had pushed himself in up to his knot in one practiced motion. The vixen's hand shot up to her muzzle, muffling a scream as the pup sheathed himself in her ass. Robyn had sometimes played with herself back there, but she never had anything bigger than a finger inside her butt. The boy went back to humping her and the vixen's cheeks turned bright red as she realized the pup had just taken her anal virginity. Worse yet his hands had left her chest and traveled further down, one teasing her clit while the fingers of the other slipped inside her still slick pussy.
Robyn was being overwhelmed by the sensations, the two little paws assaulting her pussy, the slim shaft leaking pre as it slid in and out of her ass, lubing her up for the knot that was now bumping against her pucker with every thrust, trying to lodge itself inside her. She was about to tell Tyler not to tie with her, but the kid beat her to it. One sharp thrust and one sharp burst of pain from her rear end told Robyn that Tyler was balls deep inside her ass.
"Please, honey, try and pull out... " she pleaded with the pup, feeling his cock swell inside her. She didn't want to end up stuck to him, wasn't even sure she could take having a knot up her ass, even a relatively small one.
But the sound of Tyler grunting in her ear and the sensation of cum spraying from his twitching cock told her she was too late. As the pup throbbed and spurted inside her, he gave Robyn a gentle nip on the back of her neck. This was a particularly sensitive spot for the vixen, one the kid's mother had first discovered way back in college, and it was enough to push her over the edge. Whimpery sounds were forced out of her slender muzzle as she came, her honey soaking the pup's paws.
She wasn't sure how long they stayed tied, every second seeming like an eternity to Robyn. The vixen's ears were perked up, listening with dread for the sound of Lydia's car pulling up. Fortunately, Tyler's knot went down before that, and the pup's shaft popped out of her sore rear. She got up, feeling the young cock slide all the way out of her, and turning around saw the exhausted little boy that had just come inside her.
"I love you, Aunt Robyn." The pup murmured before closing his eyes and falling asleep.
Even after everything that'd happened, Robyn couldn't help but smile warmly at the boy. 
"I love you too, honey." she whispered, kissing the top of the sleeping boy's head. Well Lydia, at least you taught him good manners...