Sir William Seton was the son of Sir Alexander Seton 1^st Lord Gordon and his wife Elizabeth Gordon, and grandson of Sir William Seton 1st Lord Seton.  He married the heiress Elizabeth de Meldrum and founded the Seton's of Meldrum, Baron's of Meldrum, Chamberlains to the Earls of Huntly and Dunfermline, as well as Chancellors of Aberdeen. The direct line ended with Elizabeth who inherited Meldrum from her uncles John and William (7th and 8th of Meldrum).