South Korea does not let gay relationships happen. With the Knowledge I have been collecting over the years, Korea would send people that were gay to jail. No evidence shows BTS is gay. Not even their personalities show Gay signs. I think it is very safe to say that non of the BTS member is gay.
There have actually been controversies on whether all or some of the BTS members are gay. However, it is wise to stay away from someone else's private live. With the little knowledge that I have about the 7 members of the BTS, based on their dispositions as in speeches and actions, I will search into my thoughts and make some things known. Starting from Kim Nam Joon, he seems so much to be straight among them. He made it known in one of his speeches that he is attracted to ladies, so that can tell he's not a gay.
As for Kim Taehyung, that is V; he seems a bit playful though, but there are no solid evidence that he is a gay. Jeon Jungkook is so boyish in action, and also interacts with girls. So, he shouldn't be a gay. I cannot really say of J-Hope; he looks more like a Bi, a very sexy guy that also seem emotional when he is with some of his group members. Kim Seokjin, Park Jimin, and Min Yoongi are the most suspectible gay, but I have no solid evidence for this.