the Battle of Falkirk, 22nd July 1298. <poem> Who fought for Wallace on Falkirk's field, John Stewart's men with sword and shield, But o'er pow'rd thus! Their fate was sealed, For freedom fell </poem>]] Marriage and issue John married Margaret de Bonkyll, the daughter and heiress of Sir Alexander de Bonkyll of that Ilk. Margaret remarried, as in 1304 she is named as wife to Sir David, Lord of Brechin. By his wife Sir John had issue: Sir Alexander Stewart of Bonkyll (d. 1319), eldest son and heir and the first "Stewart of Bonkyll," who had issue: John Stewart, 1st Earl of Angus; Sir Alan Stewart of Dreghorn (d. 19 July 1333), killed in the Battle of Halidon Hill. His descendants were the Stewarts of Darnley, the Earls of Lennox, the Seigneurs d'Abigny, and the House of Stuart who reigned over Great Britain and later the United Kingdom; Sir Walter Stewart of Garlies and Dalswinton. His great-granddaughter Marion Stewart married John Stewart of Jedworth, a grandson of Alexander Stewart of Darnley. Their descendants were the Stewarts of Garlies, later Earls of Galloway and Lords Blantyre; Sir James Stewart of Pearston (d. 19 July 1333) killed in the Battle of Halidon Hill, together with his elder brother Sir Alan Stewart. His descendants were the Stewart Lords of Lorne, Earls of Atholl, Earls of Buchan, Earls of Traquair and Clan Stewart of Appin. Sir John Stewart of Daldon (d. 19 July 1333), killed in the Battle of Halidon Hill and apparently leaving no issue. Sir Robert Stewart of Daldowie, ancestor of Steuart baronets and Seton-Steuart baronets. Sir Hugh Stewart, who died without issue. Isabella Stewart (d. after 15 July 1351), who married Thomas Randolph, 1st Earl of Moray. Royal descendants He is the direct paternal ancestor of Henry Stuart, Lord Darnley, the second husband of his brother's descendant, Mary, Queen of Scots, and of their son, James VI of Scotland, who later became James I of England in 1603. As such he was also the direct paternal ancestor of "Bonnie Prince Charlie." Genetics In 2013 and 2014, the Genealogical Studies Postgraduate Programme at the University of Strathclyde conducted a genetic study called the Battle of Bannockburn Family History Project. In this study, they tested known descendants of Sir John Stewart and his brother Sir James, which revealed the presence of a unique genetic marker on the Y chromosome of Sir John's patrilineal