Complex sentence: The owner until 2009 was Sir Reresby Sitwell, 7th Baronet Sitwell of Renishaw the eldest son of Sir Sacheverell Sitwell brother of Edith and Osbert.
Split into simpler sentences: The owner until 2009 was Sir Reresby Sitwell, 7th Baronet Sitwell of Renishaw. He was the eldest son of Sir Sacheverell Sitwell, who was brother of Edith and Osbert.