Alexander Spotswood was born in the Tangier Garrison, Morocco, Africa about 1676 to Catharine Maxwell (c. 1638 - December 1709) and her second husband, Dr Robert Spottiswoode (17 September 1637 - 1680), the Chirurgeon (surgeon) to the Garrison.

Through his father, Alexander was a grandson of Judge Robert Spottiswoode (1596–1646), a great-grandson of Archbishop John Spottiswoode (1565–1639), and a descendant of King Robert II of Scotland through the 2nd Earls of Crawford). Alexander's older half-brother (by his mother's first marriage to George Elliott) was Roger Elliott (c. 1655 - 15 May 1714), who became one of the first Governors of Gibraltar. Following the death of Robert Spotswood, his mother married thirdly, Reverend Dr. George Mercer, the Garrison's Schoolmaster.

References:

The Ancestory Of Robert E. Lee Va letters of Isaac Hobhouse Va Mag Vol 66 July 1958, #3. Historical and Genealogical Notes, The William and Mary Quarterly, Vol. 5, No. 2, October 1896, Omohundro Institute of Early American History and Culture, Jstor.org Will PRO - PROB 1/13; Official Letters (ed. by R. A. Brock, 2 vol., 1882–85); "CARRIED ON AT A VERY GREAT EXPENSE AND NEVER PRODUCED ANY PROFIT" THE ALBEMARLE IRON WORKS (1770–72) by James H. Brothers IV (2002) unpublished MA for the Anthropology Department of The College of William and Mary. Biographies by Walter Havighurst (1968) and L. Dodson (1932, repr. 1969).