I have a question and mean no disrespect against the gay population But due to recent events I am curious.?

I am friends with a Lesbian couple. They have been together about 30 years and seem very devoted to each other. They decided they wanted a child. So ‘Joan’ got herself impregnated by one of their bi-sexual friends with ‘Mary’s’ permission. She had a son. They were a very happy family. Seemed perfectly normal with the exception the child had two mothers and no father in his life. As he grew up, he announced he also was gay and had several gay relationships. He just died last month of AIDS at age 26. Joan and Mary are devastated. My question, Is being gay hereditary
,and Why do so many gay males contact AIDS ae Rock Hudson, Liberace, and etc.