My brother is also allergic to cats, among the plethora of things he's allergic to. When he visits, which is rare, he just jacks himself up with antihistamines and of course, my cats love sitting on him. If your brother isn't living with you, and visits only occasionally, I don't see why you need to find (non-existent) hypoallergenic cats.

As for kittens vs cats, that would greatly depend on your experience level. However, two things: 1. Let's not perpetuate the breeder situation - it REALLY doesn't matter what breed your cat is, it matters more for dogs depending on what you need them to work for you as, and 2. There are a lot of adult cats looking for homes in the shelters because everybody and their mother wants a kitten. Do an older cat a wonderful deed and adopt them into a forever home.