Once upon a time there was a little human girl that was taken in by the monster king of her land. People sometimes feared him, but he showed her much kindness and love, dutifully watching over her, raising her, and teaching her as the years passed. The little human grew to become quite the adventurous girl, venturing out to the local market, riding on horseback into the countryside and mingling with the people, making her beloved by all.
One night, the king slipped into her room as she slept. He had dismissed her guard and locked the door, climbing into her bed. As she awoke, she could feel him against her. The warmth of his fur and scales rubbing against bare skin as he pressed to her form. The king would hush her questioning with a soft kiss to her lips, something that he likely should not be doing as her 'father', but there was no one to stop the king, was there? 
The princess was confused by her daddy's sudden boldness with her. Admittedly, she had thoughts before. Ideas. Urges. But she knew not to act on them. But now he was here, warm and inviting and in her bed, pressing himself to her and their lips meeting, she was overwhelmed, but wanting of more. Tongue slid out to meet his lips, which parted for her, soon finding his tongue as they coiled together. Paws roamed over her human form, slipping beneath her pajamas to rub along her skin. 
As their tongues intertwined and his paws roamed, she could feel something being drawn out from deep inside of her. Small patches of scales began to appear from around her nipples beneath the pajama shirt, spreading slowly outward, causing her some alarm as they itched slightly. As her hands moved beneath her shirt, she could feel them, rough and hard contrasted with her skin, causing her to pull away from him "Daddy! What's happening?" she would exclaim, lifting her shirt to show the scales to him.
The king's eyes went wide for a moment before he shivered, realizing that his saliva had given her the right amount of his DNA to begin the change, "You...will be like me, soon." He would murmur, looking closely as the scales began to spread. His paws would gently move to them, thumbs gliding over the slick scales until they met her skin, "Soon you will have a strange urge...and we may do something more that we shouldn't, but it will bring your change to completion...and you will feel better for it."
The princess looked to her daddy King, her mind racing with thoughts. What would she look like? How would the people accept her? They all melted away as his paw shakily moved between her legs to rub her through her silken pajama pants, her young body shaking as a new and foreign feeling flooded through her. Tight little slit would begin to leak a clear fluid, her muscles tensing as he rubbed at her gently, heart rate increasing and scales spreading even more quickly along her chest. Deep down, drox urges began to awaken in her, nose suddenly attuned to the musk of his male drox pheromones, making her leak with even more urgency.
It was almost as if she was running on instinct that she turned completely to him, pressing her body against his. Lips met once again, but this time it was not a soft kiss of a father waking his daughter, but one of lust and desire. Human tongue pushed into his mouth to meet the long, nimble drox tongue which rolled along it. His paws would move back under her pajama shirt to rub over her, stomach and chest now completely coated in scales as her hands ran down his chest. She was practically grabbing at him as they kissed, her hands suddenly finding something hard, which twitched in response to her touch and caused him to flinch. The air suddenly filled with even more of his musk, causing her eyes to flash a deep hematite for a brief moment, the scales now racing up to her face and around her back, a tail and muzzle forming as her body embraced the change.
The princess soon found herself in possession of something lashing about behind her, something that soon enough responded to her thoughts and was wrapped around her daddy's waist, pulling him in for another kiss. It also had the pleasant circumstance of pushing her pajama pants down slightly, revealing a bit more of her body to her daddy. Her tongue darted out to meet his. It darted. That was odd. It was long, nimble, suddenly coiled around his as their muzzles met. A muzzle? Yes. Like his. A strange thought, something that momentarily distracted her from her head hurting quite strongly as things changed, floppy ears now atop her head instead of along the side as they had been before. 
The pain that she felt was soon overridden, though, by a fresh wave of sheer pleasure. It was in a very abnormal place, though, her lower back. Wave after wave of that pleasure washed over her, pleasure that was amplified by the contents of those vents bursting forth as if with a mind of their own to coil around her daddy king, pulling needily at his pants, tugging them before slipping inside and wrapping around his length, starting to milk out precum that caused a rapidly spreading wet spot in the material, and drawing out a long, low moan from him.
The king was soon panting in response to the attention from the princess' newly formed tentacles, his length throbbing hard against them as he lifted his hips to slide his pants off. It was then that she saw his length for the first time. She had caught glimpses of it and of his sheath before as he came from a bath or out of the large pool they shared, but it was never like this. Never throbbing, slick and oozing with what she soon identified was the source of the scent that had started driving her wild in the first place. Her tentacles would tighten around it, trying to draw more of that scent out, tongue licking over her lips as he shivered and moaned again, 
"I...we should try something." The king would murmur, his paw rubbing at her slit again before pulling away. "You should take your pants off, too. It...we are going to do something that daddies and daughters shouldn't, but...droxes are different." He would explain, watching as she complied with him and lifted her hips, slowly sliding her pants and panties off to reveal herself to him. He had thought about this moment for a long time, always quickly dismissing the mere idea of it as being wrong, but now...now that she was like him, and needy, and in need of a drox, things were different.
The king was soon upon her, pressing her back onto the bed and looming over her. Her body was almost entirely changed now, but lacked the fur that his had, the princess looking to him with questioning but lustful eyes as she felt something entirely new all over again. The tip of the king's length would press against her opening, his precum mixing with her slick honey, fur starting to spread outward from it, "Clench your teeth and try not to scream..." He would caution, pushing forward and stretching the princess open, pushing slowly into her. She had played before, yes, but this was quite different indeed.
The princess would cry out for a moment before catching herself, her honey scent and his vanilla growing stronger as her insides clenched around the invading member, the king having to hold himself back as he pulled backwards slightly and started to thrust. It was slow going at first. Though she was so slick and needy, her insides were tight, and getting deeper into her took some time. The little drox moaned out over and over, though, encouraging him on as the king began to pick up pace, now breeding with her as the fur began to spread faster and faster.
Soon the two droxes were caught in the forbidden dance between daddy and daughter. The king's hips arched over and over as more and more of his beastly length disappeared into her, and the princess? She was almost fully changed now, fur spreading down her muzzle and over her feet as each thrust drew more of her new form out. The king, his body shuddering with pleasure and need, pressed against his daughter once more, pushing deeper than ever as his knot kissed at her opening and his cocktip invaded her little womb, drawing a cry of protest that was soon silenced by his tongue in her muzzle.
He would stay there for a moment, throbbing hard inside of her, "It...it is time to complete your change, my princess." He would proclaim, pulling back slightly to begin thrusting again, now invading her womb over and over as he throbbed heavily. It only took a few more thrusts in that position to tip the king over the edge, his howl sounding through the castle as his cum rocketed out and quickly filled, then overfilled, her little form, splattering out onto the bed. That same cum completed her transformation as it entered her body, causing her mottled fur to turn a deep black, eyes changing as well as he drew out the inner lust and need that she had for her daddy.
The king would remain there like that for a long moment, pools of his need gathering on the princess' sheets. He would finally move down to his side next to her, remaining deep in her form, holding the drox daughter he had created against him, "That...is what drox daddy and daughter do. You are such a good drox...you will be good for your daddy king." He proclaimed, kissing her again and licking along her lips, looking into her deep dark eyes as they laid there in the moonlight, the room heavily scented of their copulation and his body shaking.