So my grandpa was John M Doe and his son (my uncle) is John M Doe as well -- so he's technically junior but I never have really seen him go by that designation (probably because my grandpa went by Jack, not John).
So grandpa dies and my uncle names his kid John M Doe as well, so he's the third, technically.
So should the invitation read:
Mr. and Mrs. John M Doe, Junior
Kid #1, Kid #2, John M III
Or should I just leave the junior/III designation off entirely?