Your sexuality develops during puberty, so nobody is born gay or straight. Genetics does play a part, but I also think it has a lot to do with environmental factors. It would be interesting to see, down the line, if the proportion of children later identifying as gay or bisexual increases in homosexual parent families. And also while people do not choose to have certain feelings, they may choose to act on those feelings and explore and develop them further. The home environment in which you were raised could influence this.