Ok complicated situation, will try to keep this short.
My family live in the UK, I live in another country with my DH and our 2 DDs. We do Christmas turn about with DH's family and mine. This year is our turn to go to the UK.
My parents are divorced and my mother suffers from depression. Because she cannot really cope with doing Christmas dinner and because she has a small house, Christmas Day is generally spent at my (only) sister's house. In the past my sister and her DH have made it very clear that they prefer things this way as they find it very hard to be around my mum when she is stressed.
To add to things my BIL has been diagnosed with Bipolar disorder in recent years. He finds noise, kids, family gatherings and so on stressful. He does however manage to work and lead a relatively normal life much of the time.
So this Christmas we are coming to the UK and were invited to my sister's as usual. However in between time my sister and her DH have invited my BIL's parents for Christmas Day. Every year they say 'no' but for some reason this year they have said 'yes'.
So, my sister called the other day to say that we cannot spend Christmas Day together because her DH cannot cope with us plus his parents.
So we will be going to the UK to not spend Christmas together and for the kids (2 for me and 2 for my sister) to not be together, (which really was the whole point).
In addition my bitter, depressed, mother does not like my DH (or any man really) and we will be forced to spend Christmas Day like 3 lemons sat round a meal that she will very much resent cooking whilst my sister and her 2 kids will be sat less than 10 minutes walk away.
Sorry for very long OP but wanted to be clear about the situation.
So my question is; is it unreasonable of me to be upset enough about this to try to change the situation by explaining to my sister and her DH that we are coming over to see them and their children and that we are very very disappointed to be uninvited like this?
I appreciate that it is very difficult for my sister as she is in the middle of all this and scared to upset her DH.