Giving the elder royal a kiss on the cheek, the pair were pictured greeting each other as Sophie's husband, Prince Charles' brother Prince Edward, stood watching.
WATCH: Charles and Camilla arrive in style at the Commonwealth Games in Birmingham
Edward is vice-patron of the Commonwealth Games Federation, and he released a message ahead of the event's opening ceremony, saying in part: "The Games are more than just about sport, they are the greatest manifestation of the Commonwealth: our extraordinary collection of countries linked together through a myriad of bonds of common interests and relationships."
Commonwealth Games medal winners Tom Daley OBE, Kim Daybell, Max Whitlock MBE, Galal Yafai, and Alex Danson-Bennett MBE were official baton bearers at the opening ceremony, which was broadcast on BBC One.
Each of the athletes taking part represented a cause close to their hearts.
Diver Tom showed his support of LGBTQIA rights, while Max backed mental health.
Sophie greeted her brother-in-law with a kiss
Charles was representing his mother the Queen, who is not attending the Games due to her ongoing mobility issues, Buckingham Palace previously announced.
At the opening ceremony, the Prince read the Queen's message for the Games, which she placed into the Commonwealth Games Baton back in October 2021 and which has traveled the globe during a 294-day journey to all 72 nations and territories of the Commonwealth.
Addressing the crowd on behalf of the Queen, Charles said: "Over the years, the coming together of so many for the ‘Friendly Games’ has created memorable shared experiences, established long standing relationships, and even created some friendly rivalries. But above all they remind us of our connection with one another, wherever we may be in the world, as part of the Commonwealth family of nations."
Charles addressed the crowd
He concluded: "I wish each athlete and team every success. Your hard work and dedication, particularly in recent times, have been an inspiration to all of us. It now gives me the greatest pleasure to declare the 22nd Commonwealth Games open."
The Games will run until Monday 8 August and promise to be the biggest sporting festival in the UK since the London Olympics a decade ago. Over the next 11 days, more than 5,000 athletes from 72 nations will compete in 280 events across 19 sports.