Note that while in London, the opera opened as "Leila", the 'pescatori di perle' of the title are both male!
It has frequently been remarked that there are few male duets in the traditional Italian opera repertoire.
This is presumably because of the absence of any loving relationships between males in their plots -- if we except Britten's "Death in Venice", which, while set in Italy, is hardly Italian!
Males singing together in opera, other than as a chorus, are usually those in competition or conflict, if not outright battle.
The exception that proves this rule is the often quoted 'Duet' in "I pescatori di perle" by Giorgio Bizet, where the two male friends, the pearl fishers of the title, Nadir (tenor) and Zurga (baritone), recall when they were both in love with the same female, now a 'sacerdotessa' consecrated to Brahma.
As a result of this, Nadir and Zurga chose to renounce Leila in order to remain friends.
There is a homosocial element in this, and most critics agree that while "I pescatori" can be seen as involving a love triangle, it is Nadir's betrayal to his oath of virile friendship to Zurga that leads the plot.
Such sensible behaviour of an oath renouncing the love of a female was presumably acceptable in 19th century La Scala (the opera opened in Milano in 1886) because "I pescatori" is set in an exotic non-European location (Ceylon) -- although the original libretto was set in Catania!
The same situation in a European location (if perhaps not Catania!) would have inevitably involved a duel and death, such as that portrayed in Eugene Onegin -- which ain't Italian either then!