My two children do not get along AT ALL. The youngest is a rule following autist, the eldest is a PDA autist with added Adhd and has taken advantage of the youngest many times in the past. Very badly and repeatedly.
The youngest no longer wants any form of relationship with the eldest and I would feel exactly the same if I was him.
Meanwhile the eldest is heartbroken. However, it is justified, and I know it's permanent.
I'm extremely mindful of my own past situation with siblings and I want to honour the truth of their feelings without coercing the youngest into a relationship that he does not want.
Whilst acknowledging the heartbreak that the eldest feels. Mum utterly gaslit me about my sister's abuse of me and it was probably more harmful than the abuse.
Once or twice my sister would be so very overt that it was ridiculous and mum did say you were right all along about her treatment of you. But then she would go back to gaslighting again.
I'm finding it hard to navigate this. The eldest IS abusive, to everyone actually, and it has had many very serious consequences.