When the ex wife and me split up (she did, but didn't bother to file for divorce, so I had to) the first time I made a mistake in filing, so things didn't proceed, then did again. After all it took four years (yeah we could have expedited it, but we were on ok terms, so why bother)
In the end we were only divorced 4 years after we split up. Legally in my country there's a mandatory 1 year separation phase anyway.
The only sad thing, I met someone whom I was interested in in that time, and (she communicated right from the beginning) that was something of a "no go" for her.
I was quite sad about that, specifically it would have been quite easy to confirm I'm not cheating by having her talk to my ex wife for once.
The ex and me do have children, so we'll be meeting each other every now and then for the rest of our lives. I do know her new partner, she knows mine.
Talking to each other can give a lot of information in such cases. And OP would quickly find out if the guy is cheating by suggesting to all talk to each other for once. If he is blocking, I'd be careful, if he's in a similar situation than I was he'd be very happy about that idea.