Some aspects I believe they are but some others depend on the surroundings of a person's life. Where they are being raised and taught is a huge factor. But I also believe that if "they haven't come out of the closet" or don't know, it's more of an expirement/test to how your body reacts to it. How your mind reacts, and the state of happiness it brings you.
It's possible to be gay, and still believe homosexuality is a sin. It's possible to be straight and see nothing sinful about homosexuality. Let's examine this seemingly contradictary morality.
In my opinion, our moral values determine whether we are straight, gay, lesbian, bisexual, etc. These are subconscious values which we have no control over. Our ethics are set by society. Be it parents, teachers, priests, governments, etc. We automatically assume the moral values of the society, religious sect or family group we belong to, but we do not always agree with these values. These ethical values reside in our conscious mind and basically they tell us what society sees as right and wrong.
Ethics are determined by what people tell us. Morals are determined by what people do. But morals are learnt in our early years as children and what we see, doesn't always make sense to us at that age. Later we may not even remember the things we saw, but they are there. In our subconscious. And they are what will determine our tastes when we grow up.
What exactly causes sexual attraction towards males or females or both is still a mystery, but its not genetic and we can't change it.
We can however change our ethical beliefs and learn to accept people for who they really are. Stop judging others. According to Freud the only unnatural sexual position is abstinence. Any sexual act between two, or more, consenting adults is both moral and natural.
They find it out overtime. This homosexuality thing pops up particularly in puberty, as your hormones start going crazy you uncover many different things, including your interest in sex. If someone is under the age of 9 and says they're gay, they're probably just confused, or maybe even joking about it, especially since many boys under the age of 9 believe in cooties and many girls believe in boy germs.
Sexual orientation is not definitely determined at birth, because human sexuality doesn't develop for years. Personal sexuality is constantly evolving. A person's sexual preferences generally don't become serious until their teen years, and they may change many times over the course of a lifetime. This means that a person's sexuality may be established early on, and then fluctuate between attraction to one sex or another.
First, there is no "Gay" gene and there is no way to scientifically determine this as of this time.
There is a certain age when the choice is made to act on ones sexual proclivities . . . And it is their experiences and their sexual proclivities that brings them to the point in their lives where finally decide to act . . . And make that choice ! ! !