Looking at the two of them, you would never assume that Mycroft was the one with all the kinks. Greg was fairly straight laced when it came to the bedroom, but with Mycroft, and for Mycroft, he was always up for a challenge.
Mycroft had always been someone who enjoyed giving someone a challenge, pushing their limits. One night it was reliving a teenage fantasy, "Can we dress up as Batman and Robin? I'll even be Robin if you prefer." Greg still was not sure he wanted to know why Mycroft already had the costumes in his closet.
Another night he pointed out the sexual possibilities of a brolly, "Well, I don't just carry the umbrella around in case of rain, Gregory."
Greg realized belatedly that the Clint Eastwood marathon may have been a poor choice when Mycroft looked over at him, that terrifying glint in his eyes, "I have to wonder how you would look in chaps." That had certainly been an eye opening night.
He had once considered asking John if he had these same problems, but the sexual proclivities of one Holmes was enough for him, thank you very much. Plus, Sherlock was probably even stranger.
But no matter what was thrown at him, no matter how strange our out there, his response was the same, "Sure, babe."