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
Spanish is relatively the same but ricans say gracia w/o the s at the end and primo is cousin so its gracia primo .
primo maggio
primo Juan
hola primo
De tu primo(a)
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.