I've been with DH for 7 years, married for 2. DSC are all teens now (or very nearly) but were primary school age when we first met. I have a good relationship with them, they are always welcome here and we do things together as a family. But I've never met their mum. I don't have any contact with her, all practicalities like organisation and communication are done through DH.
At first she was very confrontational and basically said I had to meet her so she could tell me (and DH) what I was and wasn't allowed to do when DH had the kids. When I said I wouldn't be a part of that she withheld contact, threatened to go to court / call the police etc. She's stopped doing that now but is still very obstructive when she wants to be so it just is what it is.
She has never come to the house and she has never met our shared DC.
For what it's worth DSC have never mentioned it and are not at all bothered. She is not at all a taboo subject in our house - the kids talk about her in passing all the time. I have never once said a bad word about her - in fact I very often play devil's advocate for her when one of them is having a moan! I just have zero interest in meeting her, or feel that I have any obligation to - and at this point there doesn't seem to be much to be gained from it.
I know other stepparents who do a lot of the drop offs and communication side of things, even having mum contact them directly not their partner, so I realise I'm in the minority. I guess I'm looking for any others who haven't met dSC mum - what does that look like for your family dynamics, and do you ever see a time when things will change. Is there anything wrong with just... not??