But there are also a certain percentage that are born bisexual. When they reach puberty they can be attracted to people of either sex.

I was born Bi, from an early age I knew I wanted to get into everybody's pants. It was very confusing. I tried both ways but it was just a lot easier and more convenient to go straight and never pursue those other urges. So yeah, that happens.
"Be yourself; everyone else is already taken." Oscar Wilde