There's no nicer way to say this but...

[kılıç_mehmet]

Well, there's the 'gay uncle' hypothesis.

Both of my uncles are unmarried, and have no children. They are heterosexual. How does this differ from the "gay uncle"?
Although I must admit, I'd be reluctant to show my children to any gay relatives I had, if I had one.

If your brother is gay and contributes to the survival of your children, the genes you have in common with him will survive.

He could do this without actually being gay, or lesbian, you know. Besides, in today's conditions, openly gay people generally disassociate themselves from family members, either by choice, or by force.

Having some men in the tribe willing to go without female mates could have been handy in several ways. One that immediately occurs is that they could be trusted to stay and help protect the women without trying to steal them while the other men went out to hunt.

Well, this increasingly sounds like a "hive" type of hypothesis. All females but a single one is infertile, and have no real desire to mate with the male drones. They go off to find nourishment, while the queen reproduces with drones.
Still doesn't make the infertile female bees lesbians.

Another is that you and your gay brother or brother-in-law can team up in raising your children, for example, hunting together and both sharing the food brought back with your children.

Well, why would you need them, actually? In this type of a hunter-gatherer society, I'm not really sure that more than a single male did actually care for a single or multiple children. Besides, what really is their homosexuality good for anyways? They could have been just asexual, attracted to no one. Just like the eunuchs of the old.
And now, homosexuals want children of their own, not to look after the children of someone else.

but it may have helped them delay breeding until their bodies were better equipped to survive childbirth.

How, exactly?

And then there is the norm that gays weren't that unlikely to have children through most of history (and prehistory), and more of their children may have survived because they would tend to have fewer of them and have proportionately more resources for each of them.

How would they tend to have fewer children? If you can look after them, or if you can use them, you can have as many children as you want or need, actually. It isn't a matter of having less children because you're gay or whatsoever.
Like you have large acres of lands. But you have no one to plough through them. You need children. You need children so that you don't have to pay someone else to plough through it. Gradually, the number of children will decrease with the increase of wealth, not otherwise.