very well done, what i would have done is ask is that brother from both or half brother parents? the other thing they suggest to ask is if the parents are co-sangnious or he and his wife are.
She did explain that this is a condition that runs in families. She also said that there is about a 50% chance of him having it. I think that's all I would say too. If you start talking about autosomal dominance etc. you can easily lose your patient.
