I know a few gay men and they all say that they resisted homosexuality throughout puberty and tried heterosexual relationships, including sex, but in vain. I don't know if it is a predisposition or biological, but I believe many gays are gay more for biological than environmental reasons.
I would not believe anything they said.
There are a lot of things that feel perfectly natural that are environmentally induced. A single incident can influence your whole life, in small or big ways, but the same incident with another person's perspective may have no influence at all on him or her.
In my opinion, if you can "induce" homosexuality through child abuse or role model neglect, for example, the whole theory of genetics goes right out the window.
I don't understand the "in vain" part. In terms of physical relationships, there is NOTHING a male can do with a male that they cannot do with a female. If you put a bag on your partner's head, how would you know what it is you were having sex with, if sex consisted only of non-vaginal activity?
Moreso, it is hard to imagine that vaginal sex would be different enough from anal sex to say that one "works" for you while the other doesn't.
It is much easier to get sexual gratification within the homosexual community, and some (many) women won't participate in the other types of activities that are related to homosexuality. But that's probably not what they meant either.
If they are talking about the attraction with the other personality, then things are much more complicated. Most heterosexuals are only attracted to a small number of people anyway. And many people DO have that attraction with people of the same sex, as that attraction does not HAVE to be associated with physical sexual activity.
My theory is that those close attractions COULD lead to sex if not for the societal "taboo" of having sex with someone of the same sex. History is replete with examples of cultural differences effecting what turns people on, and what people will do with others.
Many men would love to get oral sex. Again, with a bag over the head, would one be able to tell the sex of a person providing oral sex? Probably not -- so if you can overcome the "aversion" to contact with the same sex, you can get a lot more sexual pleasure accepting the homosexual lifestyle.
Going back to attractions, people are attracted to "types", and there are very masculine women and "feminine" men. A man might be attracted to a woman that has a more manly personality than the average man does, and be a heterosexual. Actually, that begs the question -- what IS the mechanism that wires a brain so that a male-personality female would NOT be attractive to a homosexual?
We know that a man can dress up like a woman, and men will date them and go home with them and kiss them and eventually will be grossed out only when they learn the truth.
But that just means that whatever it is that is wired in the brain which causes attractions, it is NOT the actual physical being (since the dressed-up man IS a man), but rather the brain's PERCEPTION of the person (who is dressed like a woman).
So why couldn't a homosexual be happy in a relationship with a woman who has male personality characteristics and dresses more like a man than a woman?
There was just a story about a lesbian who dressed up like a man and dated women. She said the women were not gay, although many of them wanted to have sex with her after they learned the truth -- I think because they were attracted to her maleness, and women aren't taught to be grossed out by other women's naked bodies like men are.
For example, men don't have partitions in the showers because we are taught not to look at each other, while women almost always have partitions because they don't want others looking at them.
Note my comment above, click the link, read up and then you'll have a good foundation about the causes of homosexuality.