In-laws like me better

My ex got mad at me over the weekend because I’m really close with his parents still. We have kids together, and I have full physical custody so I have them unless he’s visiting. (We live in different states. Me with our kids. Him with his new girl. Still bitter about that.)

I have always been close with his parents. His mom and I are very similar in tastes, and his dad is a good guy. The kids and I haven’t been able to see them in over a year due to the pandemic. We miss them and they miss us. I text with them. Send pics. Keep them updated.

I mentioned his parents in relation to them helping him solve a problem he had and he immediately shut it down. I jokingly asked if they were having issues and he snapped. I apologized, but I don’t feel like I should apologize for having a positive relationship with my ex in-laws.

Just needed to vent, but any ideas for how to deal with this? Thanks