We just met, so I don’t know him that well, but he was honest from the beginning. He says he’s still married because of their son, and because his wife doesn’t want to get divorced right now. Apparently, South Korea has a fault-based divorce system. TIL.
For what it’s worth, I went through the same situation from the other side. We separated, but remained married for several years because she would have been uninsured otherwise.
I was in another relationship for several years before I was actually divorced. Fortunately, my first wife had a job with insurance by the time I wanted to marry my current wife, so it all worked out. And there were never any secrets to keep.
You can’t be certain about this guy without finding out more, but the situation does not necessarily mean he’s cheating.