And despite Peter and his wife Autumn Phillips confirming their decision to divorce in February, after separating in late 2019, it seems the pair could still mark the special occasion together with their daughters Savannah and Isla.
While Peter and Autumn are reportedly living separately, they have both remained living on Princess Anne's Gatcombe Park estate in Gloucestershire.
WATCH: Peter and Autumn Phillips confirm split
In a joint statement released in February, part of it read: "Both Peter and Autumn have remained in Gloucestershire to bring up their two children where they have been settled for a number of years. Peter and Autumn have requested privacy and compassion for their children while the family continues to adapt to these changes."
Following confirmation of their split earlier this year, Peter and Autumn appear to have remained friends and attended Cheltenham Festival in March, arriving at the racecourse together.
Peter and Autumn at Cheltenham Festival in March
Princess Anne and her first husband Captain Mark Phillips welcomed her eldest son Peter in November 1977, making him the Queen's first grandchild. Peter is currently 15th in line to the throne behind his mother, but is set to move to 16th place when his cousin Princess Eugenie gives birth to her first child in early 2021.
As Anne was the only daughter of the Queen and Prince Philip, her children weren't guaranteed a royal title – unlike the children of the monarch's male offspring. However, the Queen still offered courtesy titles to both Mark when he married Anne, and their children, which the Princess declined.
Peter and Autumn on their wedding day in 2008
Peter has worked for Jaguar as a corporate hospitality manager and then for the Williams racing team. He also had a role as a manager for RBS, before leaving in 2012 to become a managing director at sports and entertainment agency, SEL UK.
He married Canadian-born Autumn Kelly at St George's Chapel in May 2008, with the pair welcoming their eldest daughter Savannah in 2010 and youngest child Isla two years later.
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