See also Earls of Ross
In a genealogy of the Mackenzies contained in The Black Book of Clanranald, we find it stated that Gilleoin of the Aird, from whom the old Earls Gillanders of Ross and the Mackenzies of Kintail are traced, was the son of Macrath (McRrath). Supposing the genealogy to be correct, this Macrath would have lived not earlier than the tenth century. By that time Christianity was fairly established in the Highlands of Scotland, and as the name Gilleoin means the servent of St. John, it is not at all unlikely that Macrath also may have been so named from some family connection with the early Church in the Highlands.
See The Connection of the Macraes with the House of Kintail:
Another of the sons of Macrae of Clunes is said to have gone to Kintail. This was probably during the first half of the fourteenth century, before the family of Mackenzie was very firmly established there. He might have been attracted to Kintail, perhaps by family connections, but quite as likely by the fact that, as the Chief of Kintail was still struggling to establish his family there, the circumstances of the country might afford opportunities of distinction and advancement for a man of enterprise. It is a singular fact that each of the first five Barons of Kintail had only one lawful son to succeed him. Mackenzie being thus without any male kindred of his own blood, earnestly urged Macrae to remain with him in Kintail. Mackenzie's proposals were accepted, and Macrae settled in Kintail, where he married one Macbeolan or Gillanders, a kinswoman of the Earls of Ross, by whom Kintail was held before it came into the possession of the Mackenzies. As the Macraes and Mackenzies were said to be of common ancestry, the Baron of Kintail expected loyal and faithful support from his newly arrived kinsman, and he was not disappointed. The Macraes were ever foremost in the cause of the chiefs of Kintail, and by their prowess in battle, their industry in the arts of peace, and in many instances by their scholarly culture and refinement, they were mainly instrumental in raising the Barony of Kintail, afterwards the Earldom of Seaforth, to the important position it occupies in the annals of Scottish history.