In the Book of Mason, Your sexuality is determined by the gender of the people you find sexually attractive regardless of who you choose to date or marry. As we speak there are probably hundreds of gay men reciting their empty vows to unfortunate women everywhere. But that doesn't change the fact that those men are gay. You see, sexuality isn't based on dating patterns or marriage certificates, it's not even based on the sexual activities you participate in. People have sex for various reasons, some do it for money, some for love, some for lust, and the list goes on. So in my opinion, sexuality is based on what you physically desire. Particularly who turns you on, who you instinctively lust after, and who you fantasize about.