Earl William died about 1481, surrendered the title and jurisdiction of Orkney in 1471, and five years later - 1476 - abdicated his remaining Earldom of Caithness in favour of his second son of the name of William, who was second son of his second marriage, thus passing over the claims of his eldest son William of the first marriage, who was ancestor of the Lords Sinclair of Ravenscraig, now reputed extinct in the male line, as also the claims of his second son, Sir Oliver St.Clair of Roslin, eldest son of the second marriage, ancestor of the St.Clairs of Roslin.
By his first wife, Elizabeth Douglas, Countess-Dowager of Buchan and of the Garioch (dead in 1452) the Earl had:
WILLIAM Prodigue, "the Waster", Master of Orkney and Caithness, to whom during his life he had given the Barony of Newburgh in Aberdeenshire. This William of Newburgh was ancestor to the Lords Sinclair and they of Warsetter, of Tohop, Saba and Grottsetter, whom see.
KATHERINE, married to Alexander, Earl of March, Duke of Albany, second son of King James II, but sentence annulling the marriage between the parties was pronounced by the official of Lothian (2nd March 1477-8) on account of propinquity of blood. They had one son Alexander, who married Margaret, daughter of the Lord Crichton, and had a daughter Margaret, married to David, Lord Drummond. [From Nisbet's Heraldry]. In a parliament held in presence of his younger brother John, the Governor, Alexander of Albany, affirmed his claim to the succession failing James V; yet notwithstanding his challenge, being more fit for a cowl, gave over all title he had in his brother's favor, whereupon to deprive him ever hereafter of lawful succession, they turned him into a priest. He had first the priory of Whitherne in Galloway; afterwards the abbey of Inchaffray; then that of Scone; was consecrated bishop of Moray, 1527, and dying in 1534 was buried at Scone.
By his second wife, Marjory Sutherland, Earl William had several sons and daughters:
SIR OLIVER, founder of the cadet branch of the St.Clairs of Roslyn, the Sinclairs of Pitcairn, Ethay, etc.
WILLIAM II, founder of the cadet line of Sinclairs, Earls of Caithness.
JOHN, Canon of Glasgow, 3rd July 1480; Bishop-nominate of Caithness for 24 years. John Sutherland, slain at Wick, 1569, was grandson to his daughter Katherine. [History of Caithness; notes]
SIR DAVID of Swynbrocht, knight, Foud of Shetland, etc., who left issue.
ALEXANDER, mentioned 1498 and 1506
GEORGE, mentioned 1498.
ROBERT, mentioned 1498 and 1504. On the 27th February 1506-7, he receives a royal grant of house and land in Edinburgh with annuity.
ARTHUR, mentioned 1498 and 1504.
ELEANOR, married John Stewart, Earl of Atholl, half-brother of James III (mentioned 1480).
ELISABETH, wife of Sir John Houston, of Houston.
MARGARET, married Sir David Boswell of Balmuto, styled of Glasmouth in a record 16th February 1492-3 (Exchequer Rolls).
EUPHEMIA.
MARJORIE, married Andrew Leslie, Master of Rothes.
MARIETTA
The seniority of the sons of the second marriage though undetermined, is probably in accordance with the order here given.
NOTE - The last Earl of Orkney had by each of his two marriages a son named William. See page 167 for two brothers Sinclair, each named Laurence; and on page 295 there are two each named William. This confusing custom occurs in other Scottish families, but only with brothers-uterine.
