Complex sentence: The by-elections were triggered by the resignation of five members of the Legislative Council, one each from the territory's five constituencies, three of them were representing the League of Social Democrats, and the other two from the Civic Party.
Split into simpler sentences: The by-elections were triggered by the resignation of five members of the Legislative Council, one each from the territory's five constituencies. Three of them were representing the League of Social Democrats, and the other two from the Civic Party.