Weeks after Spain’s King Felipe IV tested negative for coronavirus, his cousin Princess Maria Teresa de Borbon-Parma has died from the highly-contagious illness.

The death of Maria Teresa — dubbed “the red princess” due to her progressive politics and activism — was announced Thursday by her brother, Prince Sixto Enrique de Borbon, the Duke of Aranjuez.

“On this afternoon… our sister Maria Teresa de Borbon Parma and Borbon Busset, victim of the coronavirus COVID-19, died in Paris at the age of eighty-six,” he wrote.

Born in 1933, Maria Teresa was educated in France and became a distinguished professor at Paris’ Sorbonne and a professor of Sociology at Madrid’s Complutense University. An advocate of women’s rights and socialist ideas, she also studied Islam specifically as it pertains to evolving women’s rights in Arab nations, People reports.

Great Britain’s Prince Charles, 71, tested positive for coronavirus this week and is self-isolating with “mild symptoms,” his Clarence House office announced Wednesday.

The Prince of Wales’ wife, Camilla, 72, the Duchess of Cornwall, has tested negative for COVID-19.