Margaret, known as Peggy was born in 1889, the eldest child of Archie MacIsaac and Mary Ann Munro of 1 Kyles Paible, North Uist. Following their mother's death in 1906, the children stayed with their relatives in Ruisgarry on the island of Berneray.

Peggy became a domestic servant and died of tuberculosis at Brusda (the home of her maternal grandparents) aged just 24 years.