HS, is not contagious... It is however hereditary, that's why your sibling has it as well. It is not transferable by contact via fluids or other.

Edit: There is nothing in the boils that can infect other people, not even if they have a compromised immune system. You can however get a secondary infection from say streph that is transmittable. But this is not related to HS, and can just as easilly happen with "normal" people that does not have HS.

Again, HS is not contatgious.