Parents and parenting play a role. So probably do genes, hormones, birth order, abuse, seduction, chance, habit.
But a lot of parents who understood and tried to avoid all the stereotypes -- tried not to be smothering and overprotective or distant and emotionally unavailable or brutal and abusive or judgmental and hypercritical -- still ended up with homosexual children.
From that I conclude that it has to be more complicated than people assumed a generation or two ago.
It is more complicated however the “born this way” tack is totally rigid and ultimately there is a choice to act on homosexual desires and decide to live as a homosexual or whatever type of sexual person you desire. Its not just parents, its not all biology because biology is just the machine, its a combination of things. I know one person personally whose first sexual encounter was being molested as a young man by his uncle. Those that would dismiss this event as not contributing to his sexual orientation are in denial. Does that mean that all gays are molested no but its pretty clear that being sexually abused is more common for gays than the general population. I’m familiar with the hormonal research and morphology research and the genetic research and epigenetic research. The biological contribution for homosexuality is about as predictive as it can be for other behavioral traits which is somewhere in the range of 20-30% which suggests a strong environmental component. Also regardless the degree of causality of the biological component it does not explain the tendency of gay males especially towards obscenity,sexual exhibitionism, rampant promiscuity, and far too much tolerance for blurring the lines where underage males are concerned. I totally support being tolerant but this doesn’t mean the whole of society should be redesigned to elevate and norm homosexuality and other sexual “deviance” at the expense of decency and heterosexual norms.