It’s been a while since I’ve studied it academically but let me do the best from what I remember. Homosexual relationships can be divided into 3 mains groups : age-stratified, gender-stratified, and egalitarian. All of the cultures in which I’ve studied homosexuality in depth mostly fit into at least one of these three categories.
Gender-stratified is (mostly) one partner is seen as feminine. Now, originally all of these people were considered gay, but as we’ve become more academically aware of transsexuality, we’ve moved some of these people into that realm, especially because in a good deal of cultures that allow the individual to become the opposite sex as much as possible, they can often marry whomever they chose. The range of “transformation” into female can vary from simply being called a woman but not really treated like one to hormones and surgery. The hijira of India are an example of a group that can involve “SRS” for males. Hijira are considered to be a “third sex” and can consist of males, intersexed people, or females. They are mostly referred to by using female pronouns and they usually dress as women. This can be compared to an attitude common in South American countries where effeminate gay men are called “women” but (most of the time) dress as male and are mostly referred to using masculine Pronouns. I have been told this varies widely across South America in acceptance, but I’ve noticed that it seems very widely practiced in Mexico. I have a gay Mexican and a gay Salvadorian coworker and the other South American workers will use a mix of pronouns to refer to them. The most common pronoun in a serious situation is “he” but when they are joking around, they use “she.” “Fag” is a common insult and then men will often tease each other by calling each other fag, even the gay ones. My gay Mexican coworker will make fun of one of my white American coworkers by saying things like, “XX, just come out and be a fag already.” One of my female Mexican coworkers said to a gay Spanish/American customer, “if you weren’t a woman, I’d date you.” What is interesting is that (as far as I have been able to uncover) only the effeminate, passive partner is considered a woman. My Mexican coworker has a boyfriend who is apparently considered straight. His boyfriend is also married with a wife and a few kids. My coworker has been married and had a few kids. He is in his late 30s and he said that in his culture, there was a really strong pressure on producing children. He was expected to produce them even though he was gay. He dutifully did his duty and now lives full time as a gay man, only dating other men. His family is accepting of him which he says wouldn’t happen if he hadn’t produced children. On the other hand, my younger San Salvadorian coworker has no plans to ever get married, despite what his family desires.
In pre-modern cultures, some gender-stratified homosexuals were required or encouraged to have children but others were not. Having sex with an effeminate homosexual did not make a man bisexual or gay, he was still considered straight. An interesting side effect of this was that a culture could officially condemn homosexuality while still tolerating the practice. As long as it wasn’t two manly men in love with each other, then it wasn’t considered “gay.”
The second group is age-stratified. This is very well known from cultures such as Greece and Japan. In these societies it was not uncommon for older men to have sex with younger, post-pubescent adolescence. It is important to note that pedophilia was illegal in both Greece and Rome. While these older men may have dated 12 year olds, most of the poems and stories written by “boy lovers” talk about how handsome the boys become as they develop more secondary sexual characteristics. I read a translated Arabic poem where the author described how beautiful the boy he was in love with became, he said that the boy’s beard was his beautiful black eyes spilling down onto his face. Sometimes this was a temporary thing, the boy had an older male lover and, when he was old enough, he took a younger male lover. However, there are also plenty of cases where two male individuals remain together for life, even though one partner is not younger or young. I read a translated Japanese story about two old men in their 80s who had loved each other since they were in their 20s or so. One of the men wore his hair in the style of a youth despite the fact that he was actually older than his partner and had lost his youth-full features decades ago. It’s also important to note that in societies that have these types of relationships, the older man is supposed to be a mentor to the younger man. If the older man were to take advantage of the younger men, he would be scorned and probably punished. Sex with the boy is permissible and maybe even encouraged but (in most societies) it is not expected. A man is not considered different if he does or does not have sex with boys, only if he remains only with “boys.” In these societies, a person who clearly prefers males usually is not required to produce children. Now, a fundamentalist might seize on this relationships and try to argue that homosexuality has a history of pedophilia and ephebophilia, but heterosexuality has faaaaaaar more cases of older men being involved with much younger partners. Furthermore, the older men/younger boys was considered more of a mentor ship than a sexual relationship.
The third group is egalitarian relationships which is what most modern people think of when they think of gay relationships. Both partners are considered equals, men, and tend to be around the same age. This was practiced in several societies including Greece (Greece had all three). There was a group of ~150 male homosexual lovers called the “Sacred Band of Thebes.” They were selected because it was assumed that lovers would fight more fiercely in order to protect each other. I think it is a very interesting case because in American culture, gay men are considered effeminate, and we would find the idea of an army of gay soldiers a joke. However, this was not the case, the Sacred Band were considered tough warriors. They fought and won many battles but eventually were defeated after being vastly outnumbered and refusing to surrender.
Now, my information dates from 2000-2001 which is when I studied this subject. I did a quick search to see if any new information/research has been developed, but it looks like most anthropologists still hold to this theory of homosexuality. When I was doing my research, the idea of homosexuality as a completely modern social construct was falling out of fashion and it appears that it is almost completely ignored except by a few dedicated individuals today.