Complex sentence: The youngest son of Louis the German and Hemma, Charles was a great-grandson of Charlemagne and was the second-last emperor of the Carolingian dynasty and the last to rule, briefly, over a re-united Frankish empire.
Split into simpler sentences: The youngest son of Louis the German and Hemma, Charles was a great-grandson of Charlemagne. He was the second-last emperor of the Carolingian dynasty and the last to rule, briefly, over a re-united Frankish empire.