His parents were married in 1708, but for three years after the wedding they had no children: the king made a promise to God that he would build a great monastery if he had an heir. The kings had the Infanta Bárbara, on December 4, 1711 and for this the convent of Mafra was built. She remained the presumed heir to the throne for two years, until her mother gave birth to a male child, Pedro who died at the age of two; but in the meantime another boy had been born, Joseph. Although Barbara was never the presumed heir again, she spent most of her life second in line to the dynastic succession.
The princess was baptized Maria Madalena Bárbara Xavier Leonor Teresa Josefa Antonia, names in honor of various saints and relatives, but she was always called Bárbara or Maria Barbara, a name never used before in the Portuguese royal family, but that was given to her in honor of the saint of the day he was born.
She was brought up in a manner appropriate to her rank and showed a love for music, a field in which she was taught by Domenico Scarlatti, a famous harpsichord player and composer.
In 1729 at the age of eighteen, Bárabara married the future Fernando VI of Spain, two years her junior; his brother José married Fernando’s half-sister, the Infanta Mariana Victoria de Borbón-Spain. Scarlatti followed her to Madrid and stayed with her, composing hundreds of harpsichord sonatas for her.
Although Barbara was not beautiful – it is said that in the first meeting she had with her fiancé, he was quite disturbed when he saw her – Prince Ferdinand fell deeply in love with her, sharing his passion for music: his death broke his heart. They had no children.
Barbara, who suffered from a severe form of severe asthma for most of her life, died in Aranjuez, Spain, in 1758, in part due to her excessive weight.