The Princess Royal's children, Peter Phillips, 45, and Zara Tindall, 42, have shared a close bond from an early age.
Their father, Captain Mark Phillips, was not given a royal title when he married Princess Anne in 1973, so Peter and Zara are not a prince and princess.
The siblings have been able to carve out their own careers and have followed in their sporty parents' footsteps, with Peter as head of partner acquisition for the sports and entertainment rights agency CSM Sport & Entertainment, and Zara, an accomplished equestrian.
Peter and Zara both reside on Princess Anne's Gatcombe Park estate in Gloucestershire and have children of a similar age.
Peter shares two daughters, Savannah, 12, and Isla, 11, with his former wife, Autumn, while Zara and her husband, Mike Tindall, have Mia, nine, Lena, five, and two-year-old Lucas.
HELLO! take a look back at some of Peter and Zara's sweetest childhood snaps together.
Time with Granny
© GettyThe late Queen Elizabeth II looks every inch the doting grandmother as she walks with her two eldest grandchildren, in 1984.
Twinning together
© GettyWe adore the almost-matching knitwear as the two cheeky-looking siblings peek out of their truck at the Windsor Horse Trials in 1985
Matching with mum
© GettyPrincess Anne, Peter and Zara all donned kilts as they arrived for a holiday in Scotland in 1985.
Bonding with their cousins
© GettyPeter and Zara had the best time as they played on a fire engine at Sandringham with their younger cousins, Prince William and Prince Harry, in 1988.
School days
© GettyBoth Peter and Zara attended the Port Regis School in Dorset, and followed in their family's footsteps by continuing their education at Gordonstoun in Scotland. The siblings also both completed their degrees at the University of Exeter
A horse and carriage
© GettyThe pair have always had a love for equestrian sports from an early age, and they look quite the experts during a carriage ride in 1992.
