Here is another perspective, he may just have zero interest in meeting you or your XW's previous life, or being apart the new extended family.
My xw wife wants me to meet OM. I can barely tolerate her presence anymore, let alone meet the dud she kicked me to the curb for. On the other side of the coin the XH of my gf wants to meet me if I am going to be around his kids. If I believe any of her stories about why they split then I am not interested. They have their Dad, I am not him, I am just their mom's BF.
You are a good dude who seems to want to bring everyone together for the benefit of your kids, which is great. That doesn't mean everyone wants to join the party.
H(37) W(35) D8, D5, S3 T20, M13 BD 8/31/18 EA Discovered 9/13/18 Mediation 10/3/18 W files for D 10/12/18 W moves out 11/10/18 EA confirmed 12/25/18 D Final 1/10/19