Your Momma took to shouting
Your Poppa's gone to war,
Your sister's in the streets
Your brother's in the bar.
The thirteens. Right On.
Your cousin's taking smack
Your Uncle's in the joint,
Your buddy's in the gutter
Shooting for his point
The cousin of this person is talking a lot of smack, or trying to start a fight with people. The cousin could get beat up or killed or end up in a terrible situation if he continues. It further enhances the tone of this poem.
The Thirteens Black