Complex sentence: The son of Robert Arbuthnot, 2nd of Haddo-Rattray and Mary Urquhart, and older brother of George Arbuthnot, 1st of Elderslie served twice as Lord Provost of Edinburgh from 1815 to 1817 and from 1821 to 1823.
Split into simpler sentences: The son of Robert Arbuthnot, 2nd of Haddo-Rattray and Mary Urquhart, and older brother of George Arbuthnot, 1st of Elderslie. Sir William served twice as Lord Provost of Edinburgh, from 1815 to 1817 and from 1821 to 1823.