A book my daughter (she'll be 3 in November) likes is Families are Forever. It uses the term birth mother. When I tell my DD her life story, I call her bmother her ai (the Marathi word for mother) and her bfather babba (the Marathi word for father), which I think is appropriate since that would have been what she would have called them if they'd been able to raise her.
I wasn't sure that she was understanding any of either her adoption story or the one in the book, but a week or so ago we had a terrible evening with her throwing a tantrum and she got sent to bed without her bath or her story (because she spent so much time having a fit). The next morning she wanted me to read that book--I think she wanted to hear the part about families being forever even when things don't go well.
Or she liked the pink cover.
