Prince Mikasa, uncle of Emperor Akihito, died of heart failure on Thursday at a Tokyo hospital, the Imperial Household Agency said. He was 100.

The prince, the oldest member of the Imperial family, was the youngest brother of Emperor Hirohito, posthumously known as Emperor Showa.

In May, he was hospitalized for pneumonia. He recovered from the symptoms but since then his heart weakened, which led to his death at 8:34 a.m. Thursday at St. Luke's International Hospital in Chuo Ward, a spokesman at the Imperial Household Agency said.