Members of the British royal family rushed to stand by Queen Elizabeth's side after doctors

said they were concerned about the 96-year-old British 

monarch's health on Thursday (8), saying she should remain under medical supervision.

The queen, Britain's longest-reigning sovereign and the world's oldest monarch, has suffered

from what Buckingham Palace called "episodic mobility problems" since late last year.

"Following further assessment this morning, the Queen's doctors are concerned about Her Majesty's 

health and have recommended that she remain under medical supervision," the palace said in a statement.

Her eldest son and heir, Prince Charles, and his wife Camilla have traveled to the royal residence in Scotland, Balmoral 

Castle, where she is staying, along with her eldest son, Prince William, officials said. Prince 

Harry and his wife Meghan Markle will also travel to the castle to stay with Queen Elizabeth.