You know, just thinking about it, I have never seen any popup like that in MCCC or the game. Are you using any other mods that affect relationships and moves, marriage, etc. autonomously?
Are you sure you have Neighborhood Stories turned off for that household. NS doesn't marry sims afaik, but it certainly will move sims and generate babies and adoptions if you have it on. I'm not sure if it will move sims in together now as I have it shut off. I haven't used it in a while, but I did try it for a while but didn't like the chaos it was causing in my save so I shut it down for the most part. Now I only have it on for the NPCs in the Other tab and only the deaths even there just so I keep getting the NPCs changing over.
Hope this helps.
