1 Alexander Glaster Gloster Born: of Glack
..... 2 Agnes Glaster b: 1436 + Alexander de Johnstone b: 1434 m: 1476
Source: Johnston, Alexander, Jr., Genealogical account of the family of Johnston of that ilk, formerly of Caskieben, in the Shire of Aberdeen, and of its principal branches. Edinburgh, 1832.
Alexander de Johnston - who in the reign of James II, got his lands of Caskiben, which were formerly held of the Earls of Mar as superiors, erected into a free barony, to be called the Barony of Johnston in all time coming, by a decreet of the Lords, which was afterwards ratified and confirmed by King James IV on 21st February 1502; and from thenceforth, the family were designed of that Ilk. He married Agnes, daughter of Alexander Gloster of that Ilk, and of Glack, a powerful baron in the district of the Garioch, in the shire of Aberdeen; and by this lady had a family of four sons 1) William 2) also named William who married a daughter of John Kieth of Auquhorsk of whom the Johnston's of Cayesmill came -the other two sons died without succession. There is contained in the records of the Great Seal a charter "Alexandro Johnestoun de eodem et Agnetti Gloster, Sponsae suae, terrarum forrestae de Cordiss" 22nd January 1498. He was succeeded by his eldest son.