Help please

I have recently purchased plants vs zombies gw2 for my 10 year old and 6 year old to play together on split screen.  But when I try to add the second xbox account it just hangs with the little flow saying loading.  researching, it says both accounts nead a paired EA account, so I tried creating a seperate EA account but am blocked because I had previously used the EA merge function for the xbox accounts a while back and now i can't unmerge. I also tried to link it as a family account but it says i can't have 2 adults listed.  So i have tried to change my age but it won't allow that either now and says to contact support...

the only way they have been able to play is if one of them uses a guest account but that means one of them isn't able to unlock progression and it is upsetting my 6 year old.

If i can unmrge the xbox accounts so that is 1:1 then I am hopeful that will solve it.

platform Xbox one X.

Thank you