A couple I knew from internet visited me for threesome a few months ago. He had not told me that he was bi (or curious). In the middle of playing, while I was giving his wife my good head and she was enjoying it, he started stroking me. Obviously, I didn't expect it from him. Though I'm straight, I didn't lose my hard on from his action. I'm not sure if his wife knew it. I just didn't want to make things more embarrassing but kept pleasuring her while he kept stroking me. Thought of sharing my experience here.