I remember reading a review in the past couple years of at least one book on this subject, a children's book. I probably saw it on Barnes and Nobel's website. If you work with the search engine you can pull a long list to wade through of possible books.
I found this one today that might be what you are looking for: Molly's Family
by Nancy Garden, Sharon Wooding (Illustrator), Sharon Wooding (Illustrator)
http://search.barnesandnoble.com/booksearch/isbnInquiry.a...
this is another one:
Daddy's Roommate
by Michael Willhoite, Michael Willhoite (Illustrator)
(Paperback)
Publisher: Alyson Publications
Pub. Date: November 1991
ISBN-13: 9781555831189
Sales Rank: 66,202
32pp
This is one on foster parents
Zachary's New Home: A Story for Foster and Adopted Children
by Geraldine Molettiere Molettiere Blomquist, Paul B. Blomquist, Margo Lemieux (Illustrator), Margo Lemieux (Illustrator), Paul B. Blomquist
This one is an adoption one:
A Blessing from Above
by Patti Henderson, Golden Books Staff, Liz Edge (Illustrator), Elizabeth Edge (Illustrator)