William and Kate arrived at the church a few minutes late Sunday. She is expecting the couple’s third child later this month.
Prince Harry and his fiancee, American actress Meghan Markle, did not attend. Palace officials said their weekend plans are private. The two will wed in St. George’s Chapel on May 19.
Prince Philip, the queen’s husband, also did not attend. The 96-year-old has retired from public duties and is seen less frequently.
Most of the royals walked down the hill from Windsor Castle to the chapel, but the 91-year-old queen arrived by car. William and Kate also took a car to the chapel.