I come from a very close-knit family. My parents have been married for over 30 years, and I have two wonderful brothers. Fifteen years ago, when my youngest brother Joe was just 7 years old, we found out he has Asperger's syndrome. At the time, there was not much research about it; my family treated Joe like everyone else.
Being an older sister has its perks, but when you are dealing with someone on the autism spectrum, there are things to consider.
1. Be careful how you tease. If you are an older sibling, you will inevitably find ways to torment your younger brothers and sisters. But, if one of them happens to have Asperger's, they may not get over the torments so easily, and likely will not understand sarcasm.
2. Realize you may never win a debate. My brother is very headstrong and insists that Donovan McNabb should have never left the Philadelphia Eagles. He has statistics to prove it. I do not. I can just argue. He can back up his arguments about everything from sports to politicians with facts and figures.