I finally had to open my eyes and admit that my sister, nephew's mother, is toxic. I had my last straw with her behaviour and I want no more contact with her. My nephew is 5 and was conceived from a donor, so me and my kids, along with my mom are his only family. We don't have an extended family either.
My son is turning 8 (my other is 17) and we live over 40 min away in a different town. My nephew and my son play together maybe once every 2-3 weeks, mostly when my sister would visit (which she hasn't for over a month and will not anymore), but my son never mentions him when the're not together. My nephew just started school and is very sociable and my sister is pretty sociable too, so I'm not worried about my nephew's social circle. My son will want to invite his friends who are already 8, going on 9, so fairly older than my nephew.
My question is: given that my nephew can not come by himself and my sister bringing him would mean supporting her presence, is it fine not to invite him? He's too young to know it's my son's bday anyway. I know it will give my sister another reason to lash out at me, but I'm thinking that if she wanted our children to have a good relationship, she would at least make efforts not to sh*t on me or at least apologize for her outbursts. Our children can see each other sometimes at my mom's place.