Mariana of Austria
Mariana of Austria was Queen consort of Spain as the second wife of King Philip IV, who was also her maternal uncle. At the death of her husband in 1665, Queen Mariana became regent for her son Charles II, the last Spanish Habsburg, and she remained an influential figure during his reign.
Mariana and Philips marriage produced five children, however, only two lived into adulthood. Their first child was Margaret Theresa, who was born onJuly 1651 just as her mother did, she went on to marry her own maternal uncle Leopold I, Holy Roman Emperor. In 1655, Mariana then had another daughter, Maria Ambrosia de la Concepcin she only lived fifteen days. During this time, there were those at court who wanted Philip to officially name his eldest daughter, Maria Theresa, as his heir, as she was already heir presumptive according to Spanish tradition. Mariana began feeling the pressure to have a son. Eventually, her first son, Philip Prospero, was born onNovember 1657, who was joyously received. She then gave birth to the Infante Ferdinand Thomas in 1658, but he died a year later in 1659.
Source: Wikipedia