Excellent overview by TIME Magazine with strategies to help typical sibs cope.

The "typically developing" siblings of autistic children are, in fact, the furthest thing from typical. Often, they are wiser and more mature than their age would suggest. And they have to be, given the myriad challenges they face: parental responsibility; a feeling of isolation from the rest of their family; confusion, fear, anger and embarrassment about their autistic sibling. And on top of all of it, guilt for having these feelings.