No, not those kinds of bears. I mean the other large, hairy mammals that run around shirtless:
This article reports the behaviors of two healthy male bears that were raised together at a sanctuary for brown bears in Kuterevo, Croatia. The authors speculate that the oral sex started as a nursing behavior, and the bears kept doing it because, well, it felt good.
NSFW photographs of hot bear-on-bear oral action can be found at Discover's Seriously, Science? blog.