We can't choose our sexual orientation because it's genetically inherent
Existentialists believe people are free and responsible agents. They have a stake in their own development through their choices and acts of free will. Things which we cannot choose are not developed but assigned before birth.
Everyone has characteristics that they’re born with. Their genetics contribute to their physical and mental state. The same can be said for sexual preference. Sexual orientation is innate. There’s a gene called Xq28 that has been said to influence sexual orientation. It’s passed from mother to son. The gene increases the feelings of same sex attraction. If there’s a gene, then people must be born with an initial sexual orientation. People have said that they’ve known they were gay since they were little. They remember having feelings for people of the same gender as them. They carry this feeling throughout their lives 'til they finally acknowledge their sexual orientation. Most of the time, it’s not just them that notice their orientation. Often, their family knows there’s something different about them as well.
The average age that children start to remember things in their life is after 3 and 4 years old. Between the time they’re born and to that age, they are very impressionable. Anything you do could influence how a child could live. That could mean a certain thing could influence the child to have feelings for the same gender. This includes their family. The gene Xq28 is not guaranteed to make men gay. The gene only increases the chances of same sex attraction, but it also influences sexual attraction in general. That means the gene does not force anyone to be gay. Those who have the gene could stay straight for the rest of their lives even if they have the gene. Sexual orientation is ultimately a choice. There are many things that could cause someone to be gay. Genetics can play a part or environment can. But no one is born that way.
[P1] People remember feeling gay when they were little. [P2] The gene Xq28 causes men to be gay.
Rejecting the premises
[Rejecting P1] Home environment could influence children to be gay. [Rejecting P2] The Xq28 gene is not guaranteed to make men gay because it influences sexual attraction, not determining it.