For those getting allergy shots for environmental allergies: do your siblings also get shots and have similar allergies to you?

I suspect my twin brother is developing allergies since he is frequently sniffing up in response to a runny nose and complains that at night it goes to his throat. Idk if he has other symptoms since he has a disability that significantly impacts his ability to communicate and recognize when things aren’t right.

I’m allergic to dust, pollens, mold, and some animal dander. I live in an old house where there is carpet that cannot be removed due to financial reasons. My brother shares a room with my other sibling who is territorial and has soft objects everywhere (which some are covered in dust). So naturally, I suspect a dust mite allergy developing.

Any stories appreciated, especially if you are a twin (or higher)!