Even if this were true, which it isn't, why is that a problem? Unless being gay is inherently bad, it shouldn't matter if someone is more likely to be gay, should it? In a related study, the children of doctors are more likely to become doctors. Is that a bad thing? Of course not. So why bring it up? By mentioning this, all you're saying is that being gay is somehow a negative thing, and that's just thinly-veiled homophobia.
You have stumbled onto a major ethical discussion about homosexuality.
There are two separate issues. One is whether to treat people who are homosexual equally; the other is whether to treat homosexuality equally, i.e., to say that 'it's no better for a child to be heterosexual than homosexual, if you had the choice'. You can agree with the first and not the second.
The first comment I'd make is that this discussion is greatly distorted by the bias people have towards their own situation. With heterosexuals making up 95% of the population, that creates a large bias towards 'heterosexual is preferable' simply because it's more like them; the shock at the difference has led to millenia of gay discrimination - jail them, kill them, and so on.
So we have to try to discuss this on more rational issues than 'tribal bias'.
It works the same both ways though - gays are not immune to a bias that homosexaulity is just as good for a child to grow into because they have more sympathy, not the facts.
Having said that:
I'd say it's in the realm of 'reasonable argument' for heterosexuals to claim that the experience of heterosexual romance leading to family and children (and marriage, if so many of them weren't outlawing that) is an opportunity that's valuable for children making heterosexuality 'preferable' if you had a choice, even if you support zero discrimination against homosexual people.
This leads to the question: if science made a pill that would prevent homosexuality in a fetus when taking by a pregnant woman, should she? Should it be allowed?
This where that 'tribal bias' is likely to become a screaming match on both sides.
Homosexuals might feel this is almost a genocide-like destruction of one natural human condition they value and hateful and destructive, while heterosexuals would argue why it's a very good idea to not have children have this 'limitation' on their sexuality and the 'heterosexual children' and such.
Interestingly, let's bring up deafness. One would thing it's not controversial that this is a disability that's unfortunate and best prevented whenever possible.
But many deaf people have said that they very much disagree - that they prefer deafness and to remove it is to deny what some would prefer. They don't want to be 'cured'.
And when you think about it, as outrageous as it sounds, it's hard not to say that it's more an assumption by hearing people who haven't thought about the deaf's opinion.
Much as some deaf people are fighting to push restoring hearing to all deaf people whenever possible (the main issue would be children who can't decide), homosexuals might well argue against destroying homosexuality in the human population. And it's an interesting ethical discussion.
Are there also benefits to homosexuality heterosexuals don't understand or appreciate? Should the tribal bias be allowed to decide the issue?