Complex sentence: The house of Rohan was a family of viscounts, later dukes and princes, coming from the locality of Rohan in Brittany, descending from the viscounts of Porhoët and said to trace back to the legendary Conan Meriadoc.
Split into simpler sentences: The House of Rohan is a family of viscounts, later dukes and princes, coming from the locality of Rohan in Brittany. There line descends from the viscounts of Porhoët and said to trace back to the legendary Conan Meriadoc.