Complex sentence: Its official flag is identical to the Walloon Flag, which is also the official flag of Wallonia, home to 80% of all Francophone Belgians; the remaining 20% reside in Brussels, which is the seat of parliament of the French Community.
Split into simpler sentences: Its official flag is identical to the Walloon Flag, which is also the official flag of the Walloons of Wallonia. Wallonia is home to 80% of all Francophone Belgians, with the remaining 20% residing in Brussels, which is the seat of parliament of the French Community.