Maybe you can start by explaining what primo means to you in English?
You can say anything you want to Primo.
COUSIN
Roberto es nuestro primo = Roberto is our cousin
You can say "gracias, prima/primo" in Puerto Rican Spanish. "Prima" is used for female cousins, and "primo" for male cousins.
primo maggio
De tu primo(a)
primo Juan
hola primo
You could say "¿Conoces a mi primo?"
You can say anything you want to him.
you can say anything it depend how you feel and you feel about him
Gracias primo.