The act of being with a person who is trying to comfort another person when you have no real reason to be there. You are not helping in the act, though you originally intended to. You appear to just be a random person sitting next to someone who is trying to emotionally comfort another.
My friend James was comforting some girl because she had a fallout with her boyfriend. I was gonna help comfort her too, but he kinda took over. I felt like I was an emotional third wheel and left them to their talking and cuddling session.