There's Ferruccio Tagliavini and Roberto Tagliavini.
And moving away from singers and onto characters, what about those similarly named bel canto heroines: Adina and Amina? Elivira is a character in I Puritani, Ernani and Don Giovanni. Rodolfo is the hero of both Luisa Miller and La Boheme. And let's not get into all those English queens, Elisabetta di Whatnot anyone?