Infanta Maria Teresa of Portugal was the firstborn child of John VI of Portugal and Carlota Joaquina of Spain, and heir to the throne of Portugal between 1793 and 1795, until her shortlived brother Antnio Pio was born.
Maria Teresa Francisca de Assis Antnia Carlota Joana Josefa Xavier de Paula Micaela Rafaela Isabel Gonzaga was born in Ajuda, Lisbon in 1793. As the eldest child of the heir to the Portuguese monarch, she was granted the title Princess of Beira . Maria Teresa was the eldest daughter of King John VI of Portugal, then the heirapparent of the reigning queen Maria I of Portugal, and his wife Carlota Joaquina, daughter of Charles IV of Spain.
Source: Wikipedia