Queen Elizabeth II was also in attendance at the service, and was accompanied to Westminster Abbey by her son, Prince Andrew.
The royal and his wife, Kate Middleton, recently returned from their eight-day tour of Belize, Jamaica, and the Bahamas.
'While relationships remain complicated between the once inseparable brothers, there is still a rift,' a source tells ET.
The Duke and Duchess of Cambridge are continuing to face criticism as they carry on their royal tour through the Caribbean.
'It should never have happened,' the Duke of Cambridge said.
The Duchess of Cambridge attended a dinner hosted by the Governor General of Jamaica alongside her husband, Prince William.
The royal couple visited Jamaica as a part of their tour of the Caribbean in honor of Queen Elizabeth's Platinum Jubilee.
The Duchess of Cambridge is pretty in pink during her trip to Belize with husband, Prince William.
The royal couple are currently on an official eight-day tour of the Caribbean.
Kate Middleton and Prince William showed off their dance moves during their royal tour of the Caribbean in Belize on Sunday.
The royal couple's first day of outings came after they had to adjust their schedule following protests surrounding their visit.
The Duke and Duchess of Cambridge were supposed to visit the indigenous region of Belize.
The royals attended the 1st Battalion Irish Guards' St. Patrick's Day Parade in Aldershot, England.
The Duchess of Cambridge also offered the volunteers homemade cookies.
