William, who held lands within the barony of Bothwell (LAN) attached his seal on 28 August 1296 at Berwick and the following year, he had angered Edward I so much that he was fined four years’ rent for his estates. In 1303, this William was one of the Scottish ‘ambassadors’ in France who appended his seal to a letter urging the Scots to resist Edward I should he refuse to accept the truce offered by the French. However, in February 1304, he had re-entered Edward’s peace and was granted his forfeited lands along with other Scots, including others mentioned in the 1303 letter, such as the earl of Buchan, James the Steward and Enguerrand de Umfraville. This William was perhaps a son of Alexander de Balliol of Cavers, who had at least two other sons, Alexander and Thomas, as evident from a charter of December 1316, witnessed by ‘lord Alexander de Balliol [and] lord William, his brother’. A.Beam, The Balliol Dynasty, 278.
He also held lands in Edinburgh. He appears to have witnessed two charters of John Graham as brother of Alexander de Balliol and a knight; however this may be an error for 'son', or the title is incorrect.