Complex sentence: He was an illegitimate son of Thomas Tunstall of Thurland Castle, Lancashire; his legitimate half-brother, Brian Tunstall, was killed at the Battle of Flodden in 1513.
Split into simpler sentences: He was an illegitimate son of Thomas Tunstall of Thurland Castle, Lancashire. His legitimate half-brother, Brian Tunstall, was killed at the Battle of Flodden in 1513.