Well, I must warn others not to make the mistake I made as a new-to-Asperger's parent. Don't let the in-laws think that you think this comes from their side of the family.
I tried to be careful. I tried to very sensitively ask if some of the symptoms I'm reading about are seen (by anyone else besides me) in members of the extended family. What I got was not "Wow. Yeah! That explains a lot of the struggle I've had over the years with so-and-so." There was no "So that's why no one in the family has ever been close!"
The reaction was anger. There was no grasp of the value of understanding family members better. There was no embracing of the goal to communicate with others better through this knowledge. It was "No! They don't have Asperger's Syndrome! They just have a lack of communication with others. That's very hurtful that you would suggest that. You should just accept how they are without analyzing them."
So, once again I feel like like I am going insane. I feel like an alien for wanting to communicate better, for wanting to be close, for wanting understanding in relationships with my in-laws.
I guess it was helpful in one way. It makes me believe that even more members of the family than I had thought have at least a shadow of Asperger's. I will continue my quest to learn how to communicate effectively and well with adults who have AS as I am finding that I know more aspies than I realized!