So you aren’t really being excluded by everyone.
Your brother arranges to see your father. Then your sister decides to join them. You know your brother is going. As he arranged to come see you.
Your sister clearly wants to see your father and your brother. So your sister is arranging to see them when they are together. It’s not about excluding you. It’s about seeing the people she wants to see.
She doesn’t really speak to you so doesn’t seek to go down and see her father when you are there.
You could also go visit at the same time if seeing your father and sister and brother is important to you. You knew your brother was going.
Your brother is making an effort to come see you. Has told you how it’s happened. And you have labelled him as abusive. Gaslighting is an abusive behaviour. Can you see how you are coming across as difficult? And putting your brother, who is making an effort, into a difficult position and making it out he is doing something to hurt you on purpose. Could this sort of thing be why your sister is low contact with you?
Even though you know your sister is low contact with you, you want her to visit when she knows you are? And not visit when her brother who she does speak to is there. But surely you get that she wouldn’t visit when someone she is low contact is there?
If you want family get together, go when your brother is going. Speak to your sister and find out why she continues to be low contact with you, even though she is speaking to your brother and father.
What were the reasons she wet no contact?
This isn’t about excluding you. This is about her seeing the family members she is in contact with. Do you see the difference in intention?
What would you like your brother to do? Ban her from going if he is? Refuse to go if she is going and you haven’t been invited, even though that may mean she doesn’t?
He isn’t orchestrating this and putting in effort to see you, yet you are using some quite unpleasant terms about him. Do you see how that could be perceived as being difficult? And how you being ‘so sad’ and putting it on him, might make your relationship worse?