A kid sister is a sibling who is a lot younger than you are. Born when you're already grown up.

Example: 10-15+ year age gap
My kid sister is graduating high school today. (Said by a 30 year old)
by 331104 July 3, 2018
Get the Kid sister mug.
When you were just kidding, and want to inform someone that your sisterly bond is not broken; you will still talk, from time to time.
by ___giantpotato May 4, 2020
Get the I'm kidding, we're sisters, we talk mug.