Original: Oliver Cromwell, the Parliamentarian leader who overthrew the monarchy during the English Civil War, was a descendant of Thomas Cromwell's sister, Katherine Cromwell (born circa 1482).
Simplified: Oliver Cromwell, the revolutionary leader who overthrew the British monarchy and led a short-lived republican government in the 17th century, was a descendant of Thomas Cromwell's sister, Catherine Cromwell (born circa 1482).