A hard boundary? AITA?

Any comments or opinions welcomed. (sorry about grammar, English is not my native language) I am in an former mono relationship, been open for almost 6 years, morphing from ENM to Poly for the past 2 years. It was always something we agreed without any formal list on to not date people close to us, especially since we have kids and dont want to complicate there lives at this point. 2 years ago we broke our own rule and went on double dates with fellow parents at our kids kindergarten. That was supposed to be only for fun but me and one of the other parents had a really good connection that evolved into a more serious thing. Long story short I fell in love with this person but as our kids started in the same class at school my original partner said they couldnt deal with this close connection and seeing as our kids were close this was a hard boundary for them. I had to choose and chose my family life over my new relationship. I have now been suffering hard every day for over a year, still cry every week and find myself with no sex drive or longing to date anyone else. I do still love my OP but the bitterness has also coloured our relationship. Meanwhile they are still dating someone for 1,5 years and that is going so well for them. I keep ruminating about this boundary, if its something I can accept (him having admitted that at this point this is not only about the kids but this matter in general feeling super threatening as my super strong feeling are very obvious now a year later still). What do you guys think?

I'm sorry this happened. The veto seems to be super painful. (This does happen with vetoes.) Isn't your partner sorry to see you so unhappy?
I think maybe you should do some (couples) counselling, since this situation feels like a trap.

Hi neverendingstory,

To me, you and your original partner already established that there could be an exception to this rule when you went on that double date. Also your original partner admits this isn't just about that rule, it's that they felt/feel threatened by the person they made you break up with. So not such a great reason to make that rule ironclad. That's my opinion anyway.

Regards,
Kevin T.