I too was worried about this. I also think your doc has misinformed you, crohn's has genetic tendencies, that doesn't mean its genetic, its not that cut and dry. He should know that. The info above that Tonya has displayed is really helpful and sort of explains what I'm trying to say. I too am the only one in my family with crohns and my brother has undergone testing as he had similar symptoms with muscle aches and joint swelling. Luckily he hasn't got crohns, unluckily, he has reactive arthritis instead. Hopefully, all our kids will be ok, if not (god forbid) then at least they can be helped and supported by the experts (us!)
Ruth