A "combination" as you had put it implied both nature and nurture. I had set out to inform you of how misleading you were. From what you've said, you believe that the issue is entirely nurture. You're raised gay and consciously choose to be gay.
A true "combination" is that you have a predisposition to homosexuality, and you consciously pursue it. People who don't are choosing to be straight, or bi. This may go against their particular nature, depending on how inclined they are towards "being gay".
I say your genetics are one thing, and what you believe yourself to be is often something else entirely. People can go beyond their "programming" because we're gifted with something called "sentience". I don't, however, see the need in most cases.