No desire to have relationships with my family.

My mom and brother have many mental health issues. My grandparents do as well. I do desire some relations with my grandparents. But I really have no reason to see my mom other than guilt. I don't want her around my son. She's rude and we have completely different thoughts on everything. I want to cut ties but I'm really "all she has". She is manipulative, and verbally and emotionally abusive. I have been in a horrible mood all week because I have plans to see her and my brother at a public place tomorrow. I want to break it off but my brother who is 16 is very excited because he hasn't seen me or my soon in 15 months.