Found out he's married

Ladies help! I just found out this guy I've more or less been friends with benefits The last few months is married. He's never talked about her and the one time I was in his home I never saw a trace of a woman. No shoes, pictures, clothes, make up, literally nothing!! Didn't even look like a woman decorated. I have no idea what to do. Obviously I'm not going to talk to him or see him anymore but should I tell her? I mean I don't know their relationship either but I feel wrong not saying something!