Homosexuality is prevalent in Nature as well as before Judeo-christian ideologies become the norm.
Not wanting to open a can of worms, but in ancient greece pederasty is a social norm. A young-ish male being adopted/mentored by an older man in arts of war, politics, and sex. Brotherly love is acceptable in that social context. They do reproduce, as marriage is considered an expected social duty, too, and fatherhood is good for the tribe (more manpower). Plus the warlike males tend to be successful reproductively by fertilising females of the conquered nations. But in terms of social interactions, it's mostly gender segregated: male-male, and female-female. Achilles doted on Patroclus, Hephastion on Alexander (ok, ok he's Macedonian, technically), Heracles on Ioulous. Young boys aspire to be Heroes and some will vie for the attention of their idols by perfecting their performance in combat/arts etc.
Nothing to do with nature wanting to cut down population.
Of course, any anthropologists here are welcome to correct my view, as I'm just speculating.