I woke up this morning thinking, "The boy with 100 fathers and 100 mothers." I wrote that down on a piece of paper next to my bed, as I try to do when stuff like this happens, and then attempted to fall asleep again. The sentence wouldn't leave, though, and just grew. The boy with 100 fathers and 100 mothers and the girl with one of each. I knew at that point I wouldn't be falling back into sleep.
The girl would lead a sheltered life, except for her exposure to the boy and his parents. She definitely would believe in love, and often imagines her future life. She will be an optimist, warm, sweet, caring, and intelligent, but in an innocent way. She'll like stories about princes saving princesses, but sees herself more as a princess saving a prince.
There would be plenty more characters, such as the 101 fathers and 101 mothers. The girl would have a pessimistic cat that can talk but rarely will. I think one of the sets of parents will give the boy a robot known as The Man With No DNA. The boy will refer to him as NDNA. The boy will find an old blind man in a park and develop a familial bond with him. Idunno. Other stuff too.
Anyway, I doubt I'll get organized enough to really make anything of this idea, but I gave a shot at trying to nail down what I want the boy and girl to look like. I don't think I've had much success.