I will tell you my experience with this type of thing. I am in my 40's. Years ago before the Internet it used to be personal ads in the newspaper. I always found reading them intriguing. I went through a short time where I replied to some when I was single. Never had much luck with it. But I still liked reading them and I guess maybe wondering what the women were like. Once I was married I continued to read them, never replied to anything.
Then comes along the Internet. And the on-line dating sites. They are pretty much like the personal ads in the paper, only now with pictures and a lot more details. So I became intrigued with reading them. It became almost like a fetish I guess. I never did anything but would spend time that I could have been doing something else just looking and fantasizing. I have always been attracted to asian women so I would look at sites that specialized in them, or in foreign brides ect. Still never really did much. But most of those sites you have to set up some type of profile or join, just to browse. So I started doing that.
Well when you do that then the women can send you emails, so I set up other emails that no one knew about so I wouldn't get caught. Then I started responding to some of the emails and corresponding with some of the women. It was suddenly easier than it used to be with the ads in the paper. Much easier to type a quick email then write a letter.
So as the whole thing progressed I suddenly realized I was thinking about actually meeting some of these women. And I realized that I didn't want to jeopardize the things I had so I made myself quit. It hasn't been real easy and I occasionally will look. But I try to control my urges and not do anything that would be wrong.
He probably just has these same urges to look and see what is out there and to fantasize about the other women. If you do find out it is him and confront him and he says he hasn't met up with anyone else. If you can try to believe him and tell him that you do. But that you want to stop it before it leads to anything else. That is of course if you do believe he is just curious and hasn't done anything else.