Autism, handicaps.

I think that probably depends on the girl, how badl you want her in your life, and how much her brother depends on her. If he lives with her, it's best to fully understand the consequences of marrying her - you will also be responsible for helping to take care of your brother-in-law. However, if the girl is not in any way responsible for her brother's care, then why not? Of course, you could be talking about the possible genetic consequences - such as having autistic children with her. That's an entirely different subject. Medical history is a very important aspect of marriage to consider, especially if you plan on having children. Do some research on the genetic possibilities of autism moving through generations like that, and above all be honest with the girl about your thoughts.