Complex sentence: Lord Steffon Baratheon, the father of Robert, Stannis, and Renly, perished at sea with his wife, Cassana, in sight of Storm's End, on their return from a trip to the Free Cities.
Split into simpler sentences: Lord Steffon Baratheon was the father of Robert, Stannis, and Renly. He perished at sea with his wife, Cassana, in sight of Storm's End, on their return from a trip to the Free Cities.