Ok, consider: spiderdads Fantasy au
A long time ago, Peter was just a wandering dragon.
A being of solitude who traveled the lands without a destination in mind.
For him, it was a good life.
He was his own king and didn't have to bow to some rich asshole who stole his hoard from those poor humans.
That was, till he met that little hatchling.
Hatchling was a strong word, considering that Miles was in that awkward pre-teenage phase.
It was the first time in decades rather he interacted with other people, as the boy's parents were hellbent on protecting their son from him and their surroundings.
Humans just didn't understand the way that dragons worked.
This is how he learned about Kingpin and his plans to rule over humans and monsters alike.
How he was capturing wyverns like the boy to turn them into riding animals, strapping all sense of humanity off them.
So when Kingpin tries to take his new kid, he just takes over the entire kingdom and becomes emperor.
So he gets his happy end, right?
He marries MJ, the woman who leads the resistance against Kingpin, takes Miles as much under his wing as his parents allow, and gives birth to his daughter.
Expect that Kingpin didn't like being dethroned and was already planning his revenge.
The thing with Dragons (and wyverns) were extremely loyal and loving to their hoard and family.
So he kidnaps Mayday, making it look as if the neighboring Kingdom killed her.
He knew that Peter would lose himself in his grief and start a war, whilst he could raise and gain the trust of the tiny dragon.
Kingpin knew that when he actually started his real revenge, Peter wouldn't be able to harm his own child.
The only one who knew that something was wrong was Miles.
Maybe the guilt of not having protected her drove him mad, but he knew that the little princess was still alive.
But no one was listening to him.
Not Peter. Not MJ. Not his Mom. Not his dad.
He knew that Peter was suffering and that he was making it worse by denying Mayday's death.
Miles took a plight to bring her home and till that day comes, he was going to bind his wings to his back.
Meanwhile, Peter went down the deeper end.
He lost both of his kids and was mad in grief over it.
It was at that time that he met Miguel, a human tactician who had suffered the same loss as him.
It started as a pact to gain revenge and then they lost themselves in a consensual workplace relationship whilst planning the take over of another country