Prince Philip is already in an exclusive class as he celebrates his 99th birthday on Wednesday, June 10.

In fact, the Duke of Edinburgh currently holds the title as the third longest-living British royal, having surpassed Princess Alice of Albany's age in 2019.

But two other royal family members have lived past their 100th birthdays — Prince Philip would reach this mark on June 10, 2021.

Prince Philip to join Duchess Camilla in rare public engagement.

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The longest-living British royal: Princess Alice, Duchess of Gloucester

The record for the longest-living British royal family member belongs to Princess Alice, Duchess of Gloucester. She died in 2004 at the age of 102 years, 309 days.

She had married Prince Henry, son of King George V, in 1935, and survived another 30 years after his death in 1974.

Princess Alice of Gloucester in a ca. 2001 photograph.

Queen Elizabeth, the Queen Mother reached her 101st birthday

The other royal to surpass the centenary mark was none other than Prince Philip's mother in-law, Queen Elizabeth, the Queen Mother.

She lived to be 101 years, 238 days. Born in 1900, the Queen Mum celebrated her 100th birthday surrounded by the royal family in 2000.

READ MORE: The Queen Is This Close to the Longest Reign in History

Queen Elizabeth, the Queen Mother celebrates her 100th birthday on Aug. 4 2000.

Though, he's currently the third longest-living royal overall, Prince Philip is the longest-living male British royal family member. At age 94, his wife, Queen Elizabeth II, also ranks sixth.

Her Majesty and the Duke have been living in quarantine at Windsor Castle since March amid the COVID-19 pandemic. It's been reported that they will share a low-key celebratory lunch on Wednesday in honour of Prince Philip's milestone.