He got caught and is back pedaling. THere is no other interpretation, if his GF believes him so be it. Just means he's pretty good at lying to her, or she is gullible, or both.
Maybe he never behaved as a sleaze previously, but he did now. And, of course he minds if FH knows, that is why he asked. If it's innocent, then what would there be for your FH to know?
Honestly, the question only has one meaning. Being married does not equate with, as an example, no longer being able to try bungee jumping. It does, however, equate to no sex with the asshat. But, being engaged or in a committed relationship would, IMO, equate to the same thing. He's a letch and spending any amount of time alone with him is, imo, asking for trouble at this point.
Proud Member of P.O.O.P., People Offended by Offended People