sistake 

What happens when you find out your sister wasn't a planned baby.

Me: So, my dad let slip that the condom he was wearing when he had my mom bent over the couch in the living room broke once, and that is how come I have a little sister.

Little Sister: Wait, you're telling me I was a sistake?

sistake by the_colonel 781 October 2, 2010

Sistager

It derives from "sister" and "manager". It refers to a sister who servers as a manager to her siblings.

A sistager will tell you exactly what to wear and how to speak.
My sistager answers calls on my behalf.

Sistager by Lebanesegov September 9, 2022

sistacer 

a sister eraser duh

Hey sister can you snatch me that sistacer
yeah sure sister

sistacer by Sister snatched July 26, 2018