I wouldn't be too worried about it. Doubt he's gay but he may have bi tendencies. Ask him in passing or in bed what turns him on and bring up if he'd be into playing around with another guy. See what his reaction is. It may be just a fantasy or something he likes to look at. Doesn't mean he's gay, just curious. Hell, I look at some transexual videos, doesn't mean anthing but that I like to watch differnt things to get me excited.