While I fell romantically in love with him, the most he could muster was platonic love for me combined with enjoying our sex. It was always for a big tip. Besides, it bears repeating with a few of my own pointers. Research with this population is difficult due to the challenges of reaching these men—the majority of whom keep this activity covert. They get a thrill out of controlling and manipulating others to do what they want to serve their own purposes. I will not tell him I feel that way, I will always assure him it don't bother me so he is comfortable.
It was a few days just before Thanksgiving and everyone had left campus to go home for the holiday, except for me and two other guys staying in the dorms.
Another described a 'glory hole' set up in their apartment, where anonymous men could come to get off, without knowing the gender or identity of the person on the other side. This is a slippery slope toward sexual addiction; how much is too much novelty? They are straight to me. Kudos to your brother for being strong mentally with his lifestyle.
But there are sturdy incentives in place for them to not take that step of identifying, or identifying fully, as gay or bi.