[2] Three of his brothers are known; one, William, was a prominent Augustinian canon who became abbot of Inchaffray (1430–1433 or 1435), while another, David de Crannach, was sub-dean of Dunkeld and dean of Brechin.
[6] He served as representative of the university at a Paris ecclesiastical council, 30 November 1413, which debated and denounced the arguments of theologian Jean Petit.
[6] During the same period, Crannach was a popular teacher of Scottish and other students at the university, but did not return there after January 1418 when he left for the papal court at Constance.
[7] In this era Crannach served the Dauphin Charles as a diplomat, counsellor and "household master of requests" [Watt].
[7] He was still in the service of Charles, now king, when Pope Martin V provided Crannach bishop of Caithness on 4 December 1422.
[10] By 1424 at the latest Crannach was a priest and rector of Chantenay (in Sarthe department) in the diocese of Le Mans, a canonry gained either through the university of through service to the Dauphin.
[11] It was on 7 June 1426 that Crannach was translated from Caithness to the apparently more appealing see of Brechin, vacant by the death of Walter Forrester.
[12] He was in Rome in 1426 as part of an embassy sent by the king of the Scots, James I, who wished, among other things, to secure the appointment of John Cameron as bishop of Glasgow.
He was appointed as a representative of King James to the Council of Basel in 1433, but this seems to have been done by his brother Robert de Crannach.
[14] Forrester, who perhaps thought himself entitled to the episcopal office, is said to have assaulted the bishop in church, and was subsequently excommunicated by the cathedral chapter on 27 February 1435.
[14] From 1445 onwards he appears settled in his diocese, and the evidence once again indicates Crannach's concern with securing the rights and privileges of his office and see.