Bob, pay attention:
Koumbaro/Koumbara (also seen as goumbaro/goumbara or just "gumba").
In Greek language & culture, [and I'm SURE we *stole*
it from Italy and/ or Spain] It simply means the best man and his wife at your wedding. This person/couple traditionally baptizes your first child and is/are her/his God-parents.
This is the only way to CHOOSE family in that culture.
So it has come to mean, IMHO, that Koumbaro is family by choice, not usually related by blood. It is another way of saing my PAISANO, but usually implies a much closer relationship. Like *my *homey* or someone from the same PAISA (country) as you are.
Of course in the old days the KOUMBARO could have been you BF and true love and the wife was an arranged but seemingly necessary *evil*.
(Ducks and runs for the hills).
Of course it can be used to mean a real, ethnic old-world PITA meddling narrow-minded loud-mouthed but much beloved colorful character in the family tree.
Your choice.