This really is such an interesting subject @zen-art, well written and easy to understand!
Having grown up with a gay uncle made me wonder why and it appears from new studies that genes and the environment are involved here as well. He was just so different to the other men in our family, the most kind and gentle person, not effeminate at all though, apparently the ones who are also have yet another variant gene. Quite sad especially in the old days as people ridiculed them, many still do, but people are beginning to understand.
Genetics must be a fascinating field to study!