My mum invited me over for Christmas (I'm 47) to be with her and my stepfather. I accepted, then I changed my mind, then I accepted - then she said that we were going to my half-brother's who has two small children - where my half-sister would also be.

The stepfather is someone who was abusive towards me growing up and who never accepted me as his, who I knew from the age of 3. He has mellowed a lot and is largely okay when I see him now (when he is with my mum).

I have an adult son who is going to his dad's on Christmas day, but staying Christmas eve night at my home.

My mum wants to collect me on Christmas eve day and we've arranged for her, my stepfather, my half-sister to come over and for us all to go out for a meal on Christmas eve lunchtime with my son.

The trouble is that I feel that I have this block over going to my half-brother's. He has been my mum and stepfather's favourite and they are absolutely devoted to his two children - seeing them several times a week, being part-time carers for them and taking them out on visits and buying them clothes and toys. This is in major contrast with how they were when I had my son. Some of this was partly explainable due to geography, but actually I had wanted to live near my mum when my son was very small because basically I really needed support and she had really discouraged me saying that I lived in a nice area and it would be good for my son if I stayed in it (despite me being very vulnerable having had a major breakdown and a divorce and a loss of home).

Another old wound is that she told me when I was at the point of thinking about my future in my teens, that I couldn't expect their support with my education (she worded it as I couldn't expect my stepfather to support me anymore when I was living with them at the time) and then she and my stepfather went on to support my half-siblings not only with getting a university education, but with helping them save for their first homes well into their thirties.

I know that she has made some efforts to heal things and it's been really nice when she has been kind to me. However, my stepfather, while he seems pleasant enough when I do actually see him - has never actually rung me up once in all these years and I know that their wills are divided up to make sure that I don't inherit from him.

The thing is that I'm feeling that I really don't want to 'be there' for my brother's children as Christmas day will naturally revolve around them - it's not their fault at all, but to be frank I feel bitter with everything that's happened - that I and my child wasn't valued in the same way.

My mother also told me not that long ago in the past that my brother would not trust me with his children because I have had a mental illness, and that he felt that he didn't really know me. It's pretty true about us not knowing each other very well - this has largely been because I wasn't integrated into the family and there's a 10 year age gap - I left home at age 17 because the atmosphere was so tense towards me. But I can't help feeling that my mum was really being insensitive telling me this.

So I'm thinking that it would be no loss at all to my brother if I didn't turn up and that he and his wife may even rather that I wasn't there.

But if I cancel again, my mum maybe majorly annoyed with me. I would be more keen to go if we were just at my mum's, but I don't feel I've got the emotional resources to be a support for my brother's family. Also, I'm feeling torn because my son, although he's an adult, will be alone Christmas eve night and Christmas morning.

I don't know what to do.