Jurist. Born into an Ayrshire family, Fergusson was most-likely educated at the University of Edinburgh and in Leyden. He was admitted as an advocate in 1711. In 1726 he was to marry well - Lady Jean Maitland was a grand-daughter of both the Earl of Lauderdale and the Earl of Sutherland - and the couple had fourteen children. Fergusson succeeded his father as a Baronet in 1729. He served as the Member of Parliament for Sutherland (1734-35), was appointed a Lord of Session in 1735, taking the title Lord Kilkerran, and created a Lord of Justiciary in 1749.