My grandparents celebrated their 53rd wedding anniversary over the weekend and Saturday they had a dinner with the family to celebrate. I (17m) spent the day with them on Friday instead of being there Saturday.

The reason? My half sister (25f) was going to be there. They’re basically no contact between them except for when my dad’s family gets together. My half sister shows up then and every single time the two of them fight. My mom gets involved sometimes but it doesn’t happen as often.

I talked to my grandparents ahead of time and they were okay with it. They understood why I’d choose to avoid it. The only reason they don’t is because they love their son and their granddaughter and they don’t want to lose either of them. But they know i don’t have a relationship with my half sister and it’s unlikely to ever change. So I switched my work schedule around and instead of working after school on Friday I worked all day Saturday.

My parents were super pissed when they realized I was working all day. I didn’t tell them. They figured it out when I didn’t appear at my grandparents house within 30 minutes of everyone starting. They sent me dozens of texts and that only stopped when my dad and half sister had their fight. According to grandpa the fight was one of their worst ones because my half sister’s pregnant now.

My parents tore into me Saturday night and they lectured me again Sunday (yesterday). They told me I should be there and they didn’t care about me not wanting to witness another fight. Even though my grandparents knew and didn’t care they did.

For those who want (or need) to know the background for a judgement or whatever reason. My half sister’s mom died when she was 7. My dad and the mom were separated when she died. He was already dating my mom too but there wasn’t any overlap. They’d been separated for over two years when my parents met. After her mom died she spent even more time with her mom’s side of the family but when my parents got engaged they said some crap about my mom and dad intervened and then stopped the relationship between my half sister and her mom’s family. Dad didn’t like that they were alienating the relationship between my half sister and mom before it could begin. And minimizing what my mom could be to my half sister.

My half sister never forgave dad for it and she never liked my mom. She denied having any relationship with my mom and my mom could do nothing right in her eyes. Sometimes it was because my mom was pushy but other times she was taking dad’s actions out on mom. My parents tried family therapy and all kinds of stuff but even though dad cut off her mom’s family and didn’t let her hear constant negative stuff about my mom she never gave her a chance and never wanted her around, or me. When she was a teenager she’d sneak out to see her mom’s family and it caused more fights which then caused no contact at 18. Every time we see her now it’s awkward and tense and a fight breaks out. Mostly to do with her taunting dad that his plan didn’t work and her family is more important than my mom and her pointing out that my mom is nothing to her while dad thinks she should mean something.

It gets so old, you know?

Anyway… I’m done now and I just want to know AITA?