Complex sentence: The most influential family in Rhenish Franconia was that of the Salians, the head of which early in the 10th century was Conrad the Red, duke of Lorraine, and son-in-law of Otto the Great.
Split into simpler sentences: The most influential family in Rhenish Franconia was that of the Salians. In the tenth century, the head of the Salians was Conrad the Red, duke of Lorraine, and his son-in-law, Otto the Great.