Born in Altyre, Moray, Scotland, he died in Buchan and is buried in Deer Abbey.

Upon finally destroying the Meic Uilleims in 1229, he was given the Lordship of Badenoch and the lands it controlled.

He helped oversee the construction of St Mungo's Cathedral in Glasgow and after his death, Marjory continued his work there.

Her father, Fergus, Earl of Buchan (died c.1214), had no male heirs and so in marrying his daughter to William he ensured a suitable line for his titles before his death.

[4] For the historian Alan Young, William's life, and particularly his marriage to the Countess of Buchan, marks the beginning of the "Comyn century".