Thanks for clarifying your situation, LovingRadiance. Everything you say makes sense.
I do see what you mean, that Maca should insist his lovers either never meet the kids or that they commit to being a regular presence in the kids' lives.
It sounds like Maca must be making poor choices in terms of who he gets involved with, if it results in situations in which your kids are exposed to unnecessary loss and drama??
But I wonder if you could approach the situation with your kids differently. For example, does it truly damage kids to experience loss every so often? Loss is a part of life--friends move away, baby-sitters grow up, relationships end, people drift apart.
Your kids have two parents, so it's not the same as the kids of single parents who long for a second parent and get hurt when the potential mates keep abandoning them.
I don't have kids myself, but I have many memories of adults who were temporary but fun presences in my life when I was little. There was a close friend of my mom's who took me to the zoo a lot, but she ended up having a falling-out with my mom (not over dating or anything like that) and the friendship drifted apart. I remember wondering why she wasn't around any more, and my mom explaining that the friend had gotten too busy with other things and sometimes that's just what happens and that it's okay to miss people. My mom didn't get angry on my behalf or allow me to dwell on feeling abandoned (although she herself still misses this friend 25 years later).
I don't know how old your kids are, but maybe it would help to put a positive "life lesson" spin on the unexpected departure of their father's lovers. From teachers to baby-sitters to elderly relatives to high school crushes, people just aren't always around forever.
Kids get hurt easily, but kids are also pretty resilient.
But I haven't been following your story so I might be missing a lot of key info.
Single, straight, female, solo, non-monogamous.