You can say anything you want to Primo.
Maybe you can start by explaining what primo means to you in English?
A male cousin is a 'primo.'A female cousin is a 'prima.'
Roberto es nuestro primo = Roberto is our cousin
primo maggio
De tu primo(a)
primo Juan
hola primo
The word "firstly" in French can be translated as "tout d'abord" or "premièrement".
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