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Someones kid brother, whom they refer to as a baby, despite their brothers actual age.
Older Borther: "so hows my baby brother doing?!"

Younger Brother: "Shut up, im 24"
by cornandhash January 31, 2011
A Tiny person that can be annoying and fun to pick on.
They sometimes hit you with golf clubs in an attempt to ask you to play.
When in a car they scream and have a loud annoying laugh while you watch a movie, which totaly ruins it.
Baby Brothers rarly are good,quiet, can talk, and dont ruin laptops with sticky hands and pop their mother so kindly gave to them.
Baby Brother :Waaaaaah!
Olderbro: In watching a movie,shh!
Olderbro:screw this, im nnot watching it anymore.
by Rambo1283291048 September 17, 2010