The act where two sisters, typically twins, avoid all altercations with their friends in order to spend quality time together.
Friend: "Hey, do you twins want to hang out"
Sister1: "Sorry we can't"
Sister2: "Yeah, go away. We need to go Sister Bonding"
Sister1: "Sorry we can't"
Sister2: "Yeah, go away. We need to go Sister Bonding"
by Baes rocker April 23, 2016