Yeah, I think of it as this:
1. Sparda whipped *** 2000 years ago
2. For 2000 years Sparda chilled in the human world.
3. He meets Eva, marries her, and has twins by her.
I was actually thinking about making a fic where he fell in love with a powerful mortal preistess named Evalyn and she helped him fight in the war against Mundus 2000 years ago. He marries her after the war, but Mundus put a curse on her body before he was sealed. The curse is; Evalyn can not have babies so Sparda's bloodline can not continue.
Sparda still marries her knowing this. And being only human, Evalyn eventually grows old and dies, but before that she promises Sparda that she will return to him one day. And so he waits for her. 2000 years later she is reincarnated into a woman named Eva, who is a spitting image of Evalyn.
The problem is, like every reincarnation, Eva has no memory of her past life. Plus she doesn't know Sparda is a demon let alone know that demons exist in the first place.
(Evalyn has a new body as Eva, so she can have kids now.)
I really like the idea, but im so damn lazy, who knows if i'll ever get around to writing it.