Complex sentence: The consequent by-election for his seat in the 24th Dáil was won by his second son, Brian Cowen, who went on to serve as Taoiseach from 2008 to 2011.
Split into simpler sentences: The consequent by-election for his seat in the 24th Dáil was won by his second son, Brian Cowen. He went on to serve as Taoiseach from 2008 to 2011.