Lawrence Washington (c.1718-1752) was GW's eldest living half brother, the son of Augustine Washington (1694-1743) and his first wife, Jane Butler Washington. He attended Appleby School in England with his brother Augustine and after his return to Virginia in 1738 was commissioned a captain in one of the Virginia companies raised to fight in the War of Jenkins' Ear. He served with the Virginia troops in the siege of Cartagena under Admiral Vernon in Mar. 1741. Returning to Virginia in 1742 or early 1743, he was appointed adjutant general of the colony and on 19 July 1743 married Ann Fairfax, daughter of Col. William Fairfax of Belvoir. About the time of his marriage he began the rebuilding of a house on the site of his father's earlier residence on Little Hunting Creek, naming it Mount Vernon in honor of his wartime commander. Very much a substitute father to young GW, Lawrence afforded at Mount Vernon a welcome refuge from the austere life of Ferry Farm. Lawrence's marriage into the powerful Fairfax family introduced GW to the social life of the beautiful Fairfax estate at Belvoir, some four miles from Mount Vernon, where he met the most influential segment of Virginia society. By 1749 Lawrence had served for seven years as burgess for Fairfax County and was established as an active participant in the economic expansion of Virginia. His deteriorating health, however, was of increasing concern to his family and friends. He joined the 1748 session of the House of Burgesses, which convened on 2 Mar. 1749, but on 2 May was excused from further attendance "for the Recovery of his Health" (JHB, 1742-1748, 1784-1749, 387). Apparently suffering tuberculosis, Lawrence sailed for England in the summer of 1749 to seek medical advice.
In 1751 he decided to sail for Barbados in search of a healing climate, accompanied by young GW. Lawrence found that the trip to Barbados with his brother had not produced the expected improvement in his health although he remained there some three months after GW's departure. As Lawrence wrote his father-in-law Col. William Fairfax from the island, "this climate has not afforded the relief I expected from it, so that I have almost determined to try the Bermudas on my return, and, if it does not do, the dry air of Frederick" (Sparks, Writings, 2:422). A sojourn in Bermuda proved no more beneficial, and, probably in early June 1752, he returned to Virginia. On 20 June he signed his will. He died at Mount Vernon on 26 July and was buried on the estate.
See also: Nolan, Kiera E. “Lawrence Washington.” The Digital Encyclopedia of George Washington. Accessed October 10, 2016. http://www.mountvernon.org/digital-encyclopedia/article/lawrence-washington/.