Very commonly used and inconspicuous excuse for getting out of pretty much anything. One can replace the word '
brother' with any relative that would make sense. Possible substitutes include but are not limited to:
Sister,
Cousin,
Nephew, Niece, etc.
(Guy 1) Hey Guy 2, wanna hang out?
(Guy 2) One sec... Nah, I have to take my brother to
baseball practice.
(Guy 1) Hey Guy 2, wanna see a movie with some
friends?
(Guy 2) Can't tonight, I have to take my brother to
baseball practice.
(Guy 1) Hey Guy 2, wanna play some football today?
(Guy 2) Sorry man, I can't play today. I have to take my brother to baseball practice.