Your brother from the same mother but from different fathers.
Mother Brother:
A half brother which has the same mother as you, but a different father.
by DAMANI March 18, 2007
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A phrase not to be used too often. Once this is said, the world enters a vicious downfall. The most devestating thing anyone could say.
Dan: ur mother a brother
Phill: *spontaneously combusts and the whole world implodes*
by bigmassivecuntbag March 17, 2018
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Jeoff: ur mom gay
Bill:Ur mom lesbian
Jeoff:ur granny tranny
Bill:ur pappy trappy:
Jeoff: Ur sister mister
Bill: Don't make me do it!
Jeoff: Do it pussy

Bill: ur brother mother
(The sun rams into earth)
by ursistermister5 March 20, 2018
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When you are arguing and ur friend says ur sister mister u say ur brother mother. And you win the argument.Simple as that.
Brad:Yo Carl ur mom gay
Carl:No u
Brad:No no u
Carl:Ur dad lesbian

Brad:Your mom and dad both gay together

Carl:Ur granny tranny

Brad:Ur sister mister
Carl:Ur brother mother

Brad:*evaporates*
by Carl6996 March 18, 2018
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A sister that treats a brother like their own child.
The sister trying to manhandle him pretty much shows she's a mother from another brother
by 10pm January 11, 2010
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An epic comeback in any argument. Even more powerful than "your mom gay"
guy1: "ur mom gay lol xd"
guy2: "oh yeah? well your mother is your brother!"
guy1: *dies*
by wet_cardboard69 March 28, 2018
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