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From what I know, it would appear that "Veneziano/Romano" are more like "clarifications" to the Italy brothers' country names: "Veneziano" for "Venice" (Northern Italy) and "Romano" for "Rome" (Southern Italy).

"Feliciano" and "Lovino" Vargas are their respective human names.

Italia Veneziano and Italia Romano

Feliciano Vargas and Lovino Vargas