It is two persons of the opposite sex who are always there for each other. They can not even be related but trust each other anyways as if they were 'brother and sister' These 2 persons can never lose faith in each other because they will need each other. In one way or another they will always love each other no matter what, and no one can separate them.
I love have a sister and brother relationship.
by Grid_Dzyr November 19, 2013
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Organizations that pair young kids with older "brothers" & "sisters". They spend quality time together & it makes up for not having a Mom or Dad. Great for youngsters!
{Big Sisters & Big Brothers are in practically every town & city nationwide.
by Starchylde May 21, 2016
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When you like a member of the opposite sex. Eventually wanting to be in a relationship with them, but they shut you down with the "I love you like a brother/sister"
Brother/Sister Zone:

Guy: Derpina, will you go out with me?
Girl: Derp, I'm sorry, but I love you like a brother that I've never had, and I don't want to ruin that!
by tinkerbelleh_01245 June 12, 2012
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A very close friend you trust a lot
When a brother/sister (friend) likes another so much and trusts them
by MasterOfStats January 2, 2019
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A half sibling via your father

ie from his 'spunk donation'

usually applying to promiscuous men with more than one family.
I didn't know you had a brother/sister - Oh he's my "Spunk Brother / Sister"

Underlining the fact that the relationship is not a close one.
by Big Superfuzz April 2, 2009
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My enemy.
- My brother/sister is as lank as a twig.
by Spacet September 3, 2022
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If everyone was a thought brother/sister, there wouldn't be anyone more in charge than the next, there would be no hierarchy.
A thought brother/sister must be a dream to wake up from, since people seem to want a thought leader more than they want one of those.
by The Original Agahnim February 2, 2022
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