A phenomenon in which parents allow their younger children to participate in certain activities that they did not allow their older children to participate in when they were that age.
This is an example of Younger Sibling Privilege: When Johnny turned 16, his parents told him he could not work toward earning a drivers license. When his younger brother, Timmy turned 16, his parents registered him for driving school.
by Stepman December 24, 2019
Get the Younger Sibling Privilege mug.
The younger sibiling shall always embarass the older sibiling and must also rat on them and tell their friends about the older sibilings secrets.
Younger brother to older brothers freinds: did you know that he has wet his bed 10 times this month? I'm required to tell you acorrding to the younger sibiling code.
The younger sibling code: the youngest sibling shot always embarrass the older sibling and must also rat on them and tell their friends about the older siblings secrets
by Bunyguy202 November 21, 2016
Get the younger sibling code mug.
A theory that states that all younger sisters are either ugly, retarded or mind-numbingly annoying, no matter what. Sometimes, they can be a combination of these, or all three at once. These attributes are more pronounced the greater the age difference between the younger siter and her older sibling.

If the older sibling dies, the younger sister becomes neutral until such time that a younger brother is born, in which case the Older Sister Theory will take effect.

Similar to the Older Sister Theory, if there is a not-annoying, -retarded or -ugly younger sister, then one or more of the following must be true:

1. She is not blood related
2. She has a disease
3. She has addiction problems
4. She does not really have older siblings
5. You are living a lie
Example:
Guy1 "So your sister's a total twat, huh?"
Guy2 "Why would you say that?"
Guy1 "Younger Sister Theory."
Guy3 "Bitch must die!"
Guy2 "Actually, she's not that bad."
Guy1 "Dude! Seriously?!"
Guy2 "We aren't actually related, chill out."
Guy3 "Sweet! You into voyeurism?"
by Scripul April 14, 2010
Get the Younger Sister Theory mug.
A phrase used when something will make you look and/or feel younger, referencing the movie Benjamin Button.
Duder 1: "Ok, check this rhyme. I'm a pussy fiend, you can call me a glutton. Fuck you so good you'll get younger like Benjamin Button. Got my penis"

Duder 2: "Ha ha ha ha. Keep going!"

Duder 1: "My penis got a nickname it's the fountain of youth."
by westfalia February 4, 2010
Get the younger like Benjamin Button mug.
When the older/oldest sister of a family oftens engages in a relationship out of spite of her already engaged or further advanced younger sister. Generally moves in with her new man, gets engaged, married or pregnant all within the span of the younger's term of engagement. In the long run, not a wise decision.

Most people have witnessed at least two of these instances. General outcomes of "YSS" include but are not limited too:
1. a jailed husband (physical abuse, drugs, theft, video taping women at work, etc..)
2. A miserable 6 month marriage
3. single motherhood
4. self pity
Observer #1: "Jamie moved into her man's house, got pregnant and has quit her high paying job all since her younger sister LeAnn got engaged to her her long time boyfriend."

Observer #2: "yeah, I heard her man has a ton of great qualities like...well, umm...nevermind. At least he drives a nice truck"

Observer #1: " Another victim of the Younger Sister Syndrome (YSS)"

by it's funny...unless it's you October 3, 2005
Get the Younger Sister Syndrome (YSS) mug.
On October 4th, anybody who has a younger sibling can slap them, and they cannot fight back, cry, or complain. They must accept the slap.
Older brother: Hey, guess what?
Younger brother: What?
Older brother: It's Slap Your Younger Sibling Day!
Younger brother: Fine, you can slap me.
by delta! October 4, 2021
Get the Slap Your Younger Sibling Day mug.
1. An incredibly annoying way of stating that you just don't want to tell them something; might be for personal reasons. (Knowing that you cannot get younger; it therefore means one will never tell them what you are referring to.)
Caitlynn: Why won't you look at my face when we make love!?

Me: *turns away and thinks to self "ah crap, here we go again... c'mon, think of something!* ...I'll tell you when you're younger...
by The OPB: Original Purple Belt October 11, 2010
Get the I'll tell you when you're younger mug.