This book focuses on the intensity of emotions that brothers and sisters experience when they have a sibling with special needs, and the hard questions they What caused my sibling's disability? Could my own child have a disability as well? What will happen to my brother or sister if my parents die? Written for young readers, the book discusses specific disabilities in easy to understand terms. It talks about the good and the not-so-good parts of having a brother or sister who has special needs, and offers suggestions for how to make life easier for everyone in the family.
I think when this was published it was probably ground-breaking but it definitely needs an update (or maybe I have an old edition). Be aware it is American biased so not entirely relevant to other countries.