A recent ad for the Bravo TV show “Shahs of Sunset” finds two of its male stars lazing on lounge chairs at the beach. Amid a scene of scantily clad sun worshipers, the best friends Reza Farahan and Mike Shouhed gaze at different objects of desire: Mr. Farahan at musclebound guys, Mr. Shouhed at voluptuous women.

Their distinct lusts, which may have alienated gay and straight men from each other in the past, inspire the ultimate gesture of fraternal connection: a fist bump.

“Mike and I are so similar,” Mr. Farahan said. “He has been a womanizer and I’ve been a player. In the ad, we’re having a moment, and it’s the same moment. The only difference is that I’m looking at men and he’s looking at women.”

The bond strikes the Irish author Jarlath Gregory as fresh for the culture and familiar to him. His latest novel, “The Organised Criminal,” has at its center a brotherly friendship between a gay man and a straight man.