My fiancée and I each have a child from a previous marriage, we also have a 2 year old together and there are interlocutors in place for both the older kids.
It's not an ideal situation of course, but we've worked really hard to make it work so that we are all together as a family of 5 when both kids are not at their other parents (every other weekend).
After the Christmas contact, regular weekend contact is now out of sync. When this has happened before, my fiancée always delays seeing his DC until my DC has the weekend with us (my DC lives here with us, just to be clear) which means we usually forfeit a weekend with her which is horrible but we do what we have to, to make it work.
I have asked my exp to switch weekends this time, however I have proposed he sees DC a few extra days on top of this to make up for it. Meaning exp would have a lot more time with DC.
He has refused. This now means the older kids won't see each other until the April holidays
they are both going to be devastated. They absolutely adore each other and have so much in common, they stick to each other like glue when they're together and just love each other's company.
My DC is 10. Able to vocalise his wants, but exp is manipulative and intentionally difficult so may not agree to it even with DC begging for the weekends to be switched and is unable to stand up to exp.
What do I do? Accept that the interlocutor is a legally binding contract and accept that this is how it's going to be?
Exp has already said he's not agreeing to it because of something that happened a while back. (DC got a flu vaccine against Exps wishes-he kept saying DC has a higher risk of contracting covid if vaccinated against the flu and that he'll take me to court if I dare get DC vaccinated 
) So he is doing this to punish me. He's not acting in DC's best interests.
Can he really get away with doing this just to get one up on me?