The siblings marked their father Captain Mark Phillips' 75th birthday on Friday 22 September and no doubt the family would have got together for his milestone.
The retired cavalry captain shares a close bond with his children, and last month, he was seen supporting daughter Zara at the 2023 Defender Burghley Horse Trials.
Captain Mark and son Peter are also organisers of the annual Festival of British Eventing, which took place in August.
Peter has a role as Event Director, while Captain Mark, is Course Director.
Sadly, the final day of this year's event had to be called off due to adverse weather.
Captain Mark was married to Peter and Zara's mother, Princess Anne, from 1973 to 1992.
The Princess Royal has since remarried to Vice Admiral Sir Timothy Laurence.
Both Anne and Captain Mark have had successful equestrian careers.
Captain Mark is an Olympic medallist, having won gold at the 1972 Munich Olympics as part of Great Britain's eventing team.
Anne was the first member of the British royal family to compete in the Olympic Games in 1976. She also won a gold medal in 1971 and two silver medals in 1975 at the European Eventing Championships.
Zara is also a professional equestrian – she was crowned Word Champion in Aachen in 2006 and won a silver medal at the London 2012 Olympics as part of Team GB's eventing team.
Princess Anne also revealed her daughter Zara's other sporting talent, as she appeared on son-in-law Mike Tindall's The Good, The Bad & The Rugby podcast. Find out in the clip below...
Meanwhile, Peter is head of partner acquisition for the sports and entertainment rights agency CSM Sport & Entertainment. The father of two is launching ICE at Kensington Palace in November.
Speaking exclusively to HELLO!Peter detailed how his uncle, King Charles, inspired him and his business partner Rob Derry to make sustainability ICE's core value.
Peter said: "Given the location we're at, when we came up with the concept, we wanted to drive towards the sustainability piece, but the simple fact of the matter is where we are, and whose backyard we're in. We very much have to align with their core values, and so we were aligned with the King's Earth Charter, the Terra Carta, and obviously with the Sustainable Markets Initiative, their SMI.
"That is really driving all that we are doing. So, all the way through from our suppliers to our games providers, to food providers, and so and so forth, and all of our partners as well, everyone needs to be able to sign up to the process of sustainability and how we can make a winter event more sustainable."
Peter, who finalised his divorce from Autumn Kelly in 2021, is now dating longtime friend, Lindsay Steven.
He and his former wife share two daughters, Savannah, 12, and Isla, 11.
Zara married rugby star Mike Tindall in July 2011 and the couple have three children – Mia, nine, Lena, five, and two-year-old Lucas.
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