Complex sentence: Richard Cromwell (4 October 1626--12 July 1712) was the third son of Oliver Cromwell, and was the second Lord Protector of England, Scotland and Ireland, for just under nine months, from 3 September 1658 until 25 May 1659.
Split into simpler sentences: Richard Cromwell (4 October 1626--12 July 1712) was the third son of Oliver Cromwell. He was the second Lord Protector of England, Scotland and Ireland, serving for just under nine months, from 3 September 1658 until 25 May 1659.