Son of William Logan (1708?-1760?) and Agnes McAdam (b. ca. 1712),1 sister of John McAdam of Craigengillan. Married (1763) to Margaret McAdam,2 with whom he had at least three sons (William, Quintin and Alexander)3 and three daughters (Susanna, Agnes and Jane)4
Logan was laird of Camlarg in Dalmellington Parish, Ayrshire, which he inherited from his father. In 1780 he sold Camlarg to his uncle, the Laird of Craigengillan.
- 1. William Logan Sr. and Agnes McAdam married ca. 1738
- 2. Daughter of James McAdam of Waterhead
- 3. William became a skilled musician and poet, who became a friend of Neil Gow, and who was referenced as "Major Logan" in a poem by Robert Burns. He died unmarried in 1819. Alexander died abroad. Quintin became a Captain in the 37th regiment and died in Trinidad.
- 4. Susanna died unmarried. Agnes married a Captain Wilson of the Marines. Jane married Captain Lewis Mackenzie, with whom she had at least one daughter, who married Stair Park McQuhae, a son of Boswell's old friend, William McQuhae.
Boswell met Logan at the home of Logan's uncle, the Laird of Craigengillan, on September 14, 1762, where he described him as "an honest country gentleman who understands grazing and does not want [ie. lack] sense and homespun humour".