My parents divorced years ago. This means I usually spend Christmas with my mum's side of the family one year and my dad the alternating year. He has had a couple of girlfriends over the years but he's currently single so in recent years spends the day alone when I'm not there.
Last year he ruined my Christmas Eve while I was away celebrating it with my mum's side. He blew up over the phone about the fact I forgot to send him a Christmas card (should say I also suspect my dad is undiagnosed autistic as he gets fixated on odd things) even though I bought him great presents and was due to see him on return. He still hasn't apologised but our relationship is fine again. He said he was glad we would be together this year for Christmas.
Now the spanner in the works - my mum's side wants to change the year we have Christmas together so that we can include my cousins families and their young children. This means we will go again this year to them, so two years in a row, to reset the year we see them. This will be great as Christmas is always better with the little ones and there's quite a lot of us! I have so far said I'll need to miss it as I said I'd be with my dad this year but I would rather be spending it with them. Given my dad doesn't cook though, I would rather go away somewhere so it doesn't all fall to me. At least with my mum's side we all muck in. That said my mum has asked me to think about it.
YABU - I should spend it with him this year
YANBU - I should tell my dad I'm spending Christmas with the other side but I'll see him when I get back