The woman, known as Amalia, said that when Jorge Mario Bergoglio was young, they were both just 12 years old in the Buenos Aires suburb of Flores, declared that 'he would devote his life to God if he couldn't marry her'.
However on Thursday, speaking from her home in Flores, an emotional Amalia said that the 'romance' did not prosper because of the opposition of her parents.
María Elena Bergoglio, 12 years the junior of the 76-year-old pontiff, said he never wanted to be pope and now faced a lifetime of 'infinite loneliness'.
According to the Telegraph, she conceded that 'having a brother who is a pope is a blessing from God'.
She said that it was a historic moment, as he is the first non-European pope, the first Latin American and the first Argentinian'.
Bergoglio said that she never knew anything about his young love life.
Amalia added that she has nothing to hide, as it was a thing between children and totally pure.