It is common in Italian families, especially in the boom of births that followed WWII and/or in large families with many children, to name the children for the order in which they are born. So the first child/son would be named "Primo" (first),"Secondo" for the second, "Terzo" for the third, "Quarto" for the fourth, "Quinto" for the fifth, etc.FYI, the word in Italian for cousin is "cugino/a" and not "Primo/a" as in Spanish!
https://gl.wikipedia.org/wiki/Lista_de_nomes_masculinos_en_galego