Fabiola's brother and sister-in-law King Albert and Queen Paola, who are Philippe's mother and father, also attended the sombre event as was their son Prince Laurent, who was seen in the cathedral with his children Princess Louise, ten, and eight-year-old twins Prince Nicolas and Prince Aymeric.
CLICK ON PHOTOS FOR FULL GALLERY
Royals from around the world joined the congregation as 86-year-old Fabiola, who was queen consort to King Baudouin of Belgium for 33 years, was laid to rest.
King Harald of Norway and his sister Princess Astrid, who were cousins of King Baudouin, linked arms as they walked into the cathedral.
King Carl XVI Gustaf and Queen Silvia of Sweden, King Juan Carlos and Queen Sofia of Spain, Princess Beatrix and Queen Margrethe of Denmark also turned out in the Belgian capital.
Grand Duke Henri of Luxembourg, who is cousin to King Philippe, was joined by his wife Grand Duchess María Teresa, their eldest son Prince Guillaume and his wife Princess Stephanie.
Attending the funeral from further afield were Princess Sirindhorn of Thailand and Empress Michiko of Japan.