On 18 July 1452, he went into the tent of Lord Chancellor of Scotland (Crichton), where he resigned into the King's hands his lands in Ayr including Kilmaurs, as well as the sheriffdom of Ayr, and the lands of Kilmarnock in Stirling, Finlaystone in Renfrew, Glencairn in Dumfries, and Hilton in Berwick.
On 13 January 1478, he had a charter as Alexander Dominus de Kilmaweris of his lands of Drips, in the lordship of Kilbride, Lanark.
Alexander, Lord Kilmaurs, who was then very powerful, brought his forces to aid the King's party and assisted in the defeat of the rebels at Battle of Blackness.
Alter the battle of Blackness a proposal was made for a treaty between the opposite parties, and articles were drawn up for that purpose.
The war broke out again, and on 11 June 1488, during the Battle of Sauchieburn near Stirling, Alexander Cuninghame, Earl of Glencairn was killed.
On 4 February 1479 William received from his father a charter of the lands of Craiganys (Craigends) in the lordship of Ranfurley 3.