UPDATE
I rang his wife this morning but withheld my number and we were on the phone for approx 1 hour. She was quite friendly to me but guarded about some details, as you would be I suppose and I was the same with her. She told me when she met him, he was in his mid 30s and they shared exes details and he mentioned my name and another GF he'd had when he was younger, it seems he hasn't had that many serious relationships before they got married. Funnily enough he didn't badmouth me to her but did say we were young and argued a bit but also had a good relationship at times and had some nice holidays abroad which we did have.
What has now happened is I'd come up as a friend suggestion to her on FB a while ago and she noticed my unusual first name and was slightly curious about me but as my profile is locked down she couldn't see much so she left it there at the time. I told her my relationship history (been married, divorced no kids etc) and that I was seeing someone now and therefore no threat to her which she seemed ok with. She has noticed that since the pubs have reopened recently and people can drink outside that he's been out with his mates a lot more again and she's concerned there's another woman in the picture. She told me that he's been on furlough for some of the lockdowns (I think first part) and now works from home as does she but he may be returning to the office soon. Her main reason for contacting me now was last summer when people could go out and drink etc and meet she noticed he was doing this a lot - he said he seeing friends and/or work colleagues mostly at the end of the day or in afternoons. She'd heard another woman who I know of and met once or twice had joined this group who used to work with him and apparently they had a fling together after he left the company (years ago).
His wife told me he also came home very late from being out a few times (say early hours of the morning) and once overnight back early morning. and this carried on up until Christmas but recently restarted.
She asked me straight out if he'd ever cheated on me and I told her what I'd been told by him but said that this was the only occasion I knew, as far as I was aware. She was quiet when I said this.
She also mentioned that he had a tendency to be emotionally abusive to her but had never hit her and asked if he'd done the same to me and I agreed yes, he had done, I didn't elaborate. I did say he may have changed and matured over the years as many of us do.
We both agreed that he likes a Stepford Wife type partner, e.g. one who cooks, cleans, etc for him and him doing little in return but she said she has got him to do more housework since they got together as she didn't want to be like his mum who did everything.
I did ask her what she wanted to do now, and she said she wasn't sure. She said they've got a mortgage and kids together etc but she said she was going to do a bit of digging etc, she thinks she knows his phone and ipad passwords and then go from there.
I told her I was speaking in confidence to her and I did ask her to please not mention my name if she spoke to him and I actually told her if she wished to speak to me again then I'd be happy to do so but I didn't want much else involvement or for it to get dramatic.
She did mention meeting me for a coffee and I said if she was prepared to meet half way distance wise then yes I could do this but I'd bring a friend with me and suggested she do similar. She has a friend who lives not that far from me so we may do that.
The one thing she did mention to me why she was contacting me was she knows his friends but says they're all tight knit and keep each others secrets - even the wives. She says she gets on with them but feels like there's a gap between his friends and her friends. She also mentioned to me she'd seen the mutual friend of ours in a beauty salon the other week but just to say hi to and exchange pleasantries which presumably has jogged her memory to message me.
So I suppose we'll meet up.
I don't really want to get too involved in their lives or they in mine but happy to have listened to her and she said thanks for listening to her talk and her concerns and she told me I was kind for doing so as some people wouldn't do this.