Can dating sites randomly log you in on their own?

[Dubyah]

I realize how stupid this question sounds, but I want to be sure. My mom's boyfriend has several accounts on different dating sites that she just recently found out about, naturally this upset my mother. He has stated that he hasn't been on these sites in years, but most of them say that he has been on only a few weeks ago. He has stated this was some sort of glitch and that he truly hasn't been on. He has been known to lie very frequently so it would surprise me very much if there was any truth in what he was saying, but I just wanted to be sure.