Traditionally, in socieites which accepted homosexuality, there was no equivalent of the marriage relationship for people of the same sex.

That sounds like a naked assertion not much supported by evidence. Since we were talking about Asia, here is a passage from Wikipedia talking about Japan:

From religious circles, same-sex love spread to the warrior (samurai) class, where it was customary for a boy in the wakashū age category to undergo training in the martial arts by apprenticing to a more experienced adult man. The man was permitted, if the boy agreed, to take the boy as his lover until he came of age; this relationship, often formalized in a "brotherhood contract",[11] was expected to be exclusive, with both partners swearing to take no other (male) lovers. This practice, along with clerical pederasty, developed into the codified system of age-structured homosexuality known as shudō, abbreviated from wakashūdo, the "way (do) of wakashū".[12] The older partner, in the role of nenja, would teach the wakashū martial skills, warrior etiquette, and the samurai code of honor, while his desire to be a good role model for his wakashū would lead him to behave more honorably himself; thus a shudō relationship was considered to have a "mutually ennobling effect".[13] In addition, both parties were expected to be loyal unto death...

Looks like an "equivalent of the marriage relationship", doesn't it?