Britain's Prince Philip, a constant presence at Queen Elizabeth II's side for decades, died Friday at age 99, Buckingham Palace announced. He was admitted to hospital on February 16, 2021, and went home after a month during which he was treated for a pre-existing heart condition and an infection. Philip and the queen received their first vaccinations against the virus in January. His death comes just months before his 100th birthday in June, an event typically marked in Britain with a congratulatory message from the queen, who is now Britain's longest-serving monarch. Philip and the queen have four children -- Charles, Anne, Andrew and Edward -- eight grandchildren and nine great-grandchildren.