Blended families can blur the boundaries of siblinghood, especially when an affair twists the family’s narrative.

One teenager never felt close to her half-siblings from her father’s new marriage. So when her half-sister started making demands about the invite list to her upcoming birthday party, she was forced to decide which lines she was willing to cross to keep the peace.

Read on for the full story!

AITA for telling my half sister her other half sister isn’t my family and I don’t need to invite her to my birthday parties or anything?

My mom and dad had me (16F). They broke up. Then my mom died.

All this happened by the time I was 2. My parents were never married either.

My dad had a relationship with another woman. For this post, I’ll call her Mary. My dad and Mary had my half-sister, Nova (12F), together.

Then their family dynamic got even more complex.

My dad and Mary broke up. Mary got married to a guy and had a daughter, Ava (7), with him.

I live with Dad full-time (obviously). Nova splits her time between Dad and Mary. Nova and I are half-sisters.

She doesn’t consider herself close to them at all.

Nova has another half-sister, Ava, who isn’t my half-sister or anything. I have nothing to do with Mary, Ava, or Mary’s husband.

I don’t ever speak to them or hang out with them. I’m not part of their family, and I don’t want to be.

There’s loads of lingering resentment between them.

But Nova has always hated that we have more, thanks to Dad, than Ava does. Dad always went all out for our birthdays and the parties we’d have with him.

Nova had two every year — one at Dad’s and one at Mary’s. I have one because I don’t have a mom to throw a second one for me.

I never wanted to include Mary, her husband, or Ava because they’re not my family or my friends.

Nova has always resented their lack of closeness.

But Nova got really annoyed that Dad was taking me, my friends, and some family — including her and a few cousins — to a water park for my birthday, and I wouldn’t invite Ava.

She went as far as demanding an invite for Ava, and she wasn’t going to take no for an answer.

She had asked for Ava to be invited before, and Dad always told her she could invite Ava to her parties if she wanted, but I didn’t have to if I didn’t want to.

Nova went really hard on it this time. She told me we’re all family and Ava’s basically my sister too.

I told her Ava isn’t my family, my sister, or anything to me. I said she’s some random kid.

But Nova sees things differently.

Nova told me her mom (Mary) was basically my mom for years. I said that wasn’t true and that Mary isn’t my family either.

She told me if we’re both her sisters, then we should be each other’s sisters too, and sisters should be included in parties like the water park.

So she reminds Nova that she can do whatever she wants for her party.

I told her she could pick the water park for her birthday in a couple of months and invite Ava, but I wasn’t going to.

I told her she couldn’t change my mind.

She felt strongly about this boundary and wasn’t willing to budge.

She asked why, and I said I don’t want Ava there and I don’t want Ava to be my sister. That she’s her sister and always would be, but she’d never be mine.

Of course, Nova isn’t happy and starts badmouthing her even more.

Nova’s really ticked at me, and it’s worse now that the party happened and I didn’t change my mind.

Dad’s talked to her about it, but it did no good. She calls me a mean girl and a jerk and says I’m a bad sister.

AITA?

Family drama like this would make anyone’s head swirl.

What did Reddit have to say?

It’s not fair for Ava to get a say on how her half sister chooses to celebrate her birthday.

This commenter believes someone else could be pressuring Ava to behave this way.

When it comes to complex interpersonal relationships, there’s only so much teenagers can handle on their own.

This whole situation is really something the adults in their life should figure out.

It was her birthday party and she alone should get to write the guest list.

With time and dedication, it’s possible the girls can improve their relationship, but until then, Nova and Ava will need to get comfortable with reality.

Close bonds are earned, not forced.

If you liked that story, read this one about grandparents who set up a college fund for their grandkid because his parents won’t, but then his parents want to use the money to cover sibling’s medical expenses.