I love the Papa Dofla headcanons a lot. I looked at fanart and this happened, it's not supposed to be terribly serious. It's all over the place (but it's supposed to be, I wrote it that way for a reason..), but I still rather like it. Thank you for reading!
He supposed it was a bit surprising for a child to suddenly be on the scene. After all, the warlord Donquixote Doflamingo had a bit of a threatening disposition despite his constant smiling. What use did any of them have for a child, anyway—
If anyone asked, he would tell them that there was no real use for a child. But that didn't mean that one couldn't be around. He had picked him up somewhere deep in the North Blue, a little one named Trafalgar Law. When he brought him back, plenty of his subordinates had quickly forgotten their places and laughed, saying that their master couldn't possibly raise a child correctly. Some of them had been disposed of, others simply punished … but all of them left him with the desire to prove it wrong. Why couldn't he do it? It couldn't be that hard …
He started slowly, and in all the wrong places.
A few days after arriving, Doflamingo sat himself down with the child and tried to get him to talk, offering his own name, then offering 'papa'. Vergo had walked by and shook his head. "He's too young." Doflamingo had frowned.
Dropping the idea of talking for the time being, he set his sights on walking instead. There were many a long hallway in their castle, and he picked the closest one. He was unconcerned about the plethora of priceless vases and decorations that lined the tables; after all, he was a king—nothing was priceless to him. Doflamingo stopped at one end, holding little Law by the hands and urging him to walk. It wasn't for a couple moments that he realized that the child was certainly trying to walk, but he couldn't; his tiny legs swung in the air because his pseudo-father had forgotten about his height. "Oh."
Instead of simply leaning over, he moved on to other things. The child seemed sullen, he didn't realize that it was a sign of things to come. He wasn't particularly interested in playing with many things (aside from the things that were alive—he spent much of his unconfined time crawling after the birds that roamed the estate), though he seemed to like laps and the warmth of Doflamingo's coat.
Vergo was the only other person who seemed remotely interested in the child's upbringing. He would sit in occasionally and settle Law on his lap, or sometimes he'd feed him (though they tended to try and avoid that—more of the food ended up on Vergo's face than in the child's mouth), sometimes he'd talk to him. Law's first word was 'papa', as he had been conditioned to say. It hadn't been to Doflamingo. He had been speaking to one of the actual flamingos on the premises.
Teaching the kid to walk was a major inconvenience—Doflamingo had to bend over almost completely just to keep hold of his tiny, tiny hands (Law could sit in one of his palms, he'd tried a couple days after bringing him home) and it was uncomfortable, but he understood it was something that needed to be done. The discomfort and aches in his back paid off when, one day, he was able to let go and Law went wobbling down the corridor on his own. They had celebrated that night, Law didn't do much other than gnaw on one of his toys.
Whenever he saw them, Doflamingo made sure to gloat to the people who had doubted him. Maybe the kid was a little sullen, but that could change, he assured everyone (including himself). It did, a little.
Law expressed an interest in … grotesque things from an early age. He would bring in frogs from the ponds and Doflamingo would find him in the middle of the floor, with the frogs pinned to overturned boxes and ready to cut them right down the middle. He made a point to get him some books about doctors and even went above and beyond, bringing home authentic doctor's equipment one day. Anyone who was there will tell you that little Law didn't take the stethoscope off his neck for a good two weeks.
As he grew, Doflamingo worked uncharacteristically hard to teach Law what he wanted him to know and to nurture the way he believed he was supposed to. It might not have been the proper way, but nobody spoke against it.
It was a shame, however— Doflamingo was unaware of what was to come, and the fact that the child he'd put so much effort into raising would deflect from him and go so far as to wish him dead was something he was unable to comprehend, though that time would surely come.
Errr. I'm thinking of making another chapter for this, so I'll leave it open-ended for now. Thank you, again, for reading!