Since I had such good luck finding Italian records on FamilySearch.org, I decided to look for additional Cuba siblings.
By browsing the Italy Image Only Historical Records, I found more documents from Caltanissetta, Caltanissetta, Civil Registration (Tribunale), 1866-1910.
Lo and behold, I found another sister! Guiseppa born to Luigi Cuba and Rosaria Dimenza on 3 February 1886.
Italian families were typically very large. If you are researching your Italian genealogy and can’t find a birth record for your direct ancestor, try looking for the birth records of their siblings. Italian records contain a wealth of information, such as age of parents and occupation.