Malcolm, known as Calum, born in 1896, was the son of Archie MacIsaac and Mary Ann Munro of 1 Kyles Paible, North Uist.

Following his mother's death in 1906, Calum and his siblings stayed with their maternal relatives on Berneray. He attended Berneray School for two periods between 1908 and 1910, under the guardianship of his uncle John Munro and aunt Mary of 19 Ruisgarry (Brusda), with whom he and his younger sister were living.

Calum owned a shop in Quay for several years. He later moved to 10 Ruisgarry (Gunhill). He never married. Following his death, 10 Ruisgarry was passed to his nephew.