His brothers John and Jonathan Cawthra served in the War of 1812 at Detroit and Queenston under Sir Isaac Brock, and his brother John later served as the first Member of Parliament for Simcoe County.
His brothers John and Jonathan Cawthra served in the War of 1812 at Detroit and Queenston under Sir Isaac Brock. John Cawthra later served as an MHA and as the first Member of Parliament for Simcoe County.