. Given his first marriage in c. 1497 and that he was young enough to join the Battle of Flodden Field in 1513, William was most likely born around 1475.
William inherited the family estates on his father's death in 1502. From
He was shortly after appointed steward of Monteith, and captain of the Castle of Doune in Perthshire, for, in the following year, 1503, with George, Abbot of Holyrood, Walter Scott of Buccleuch, and others, he is witness to the saisine of
Margaret of England, in the county (or district) of Monteith, in consequence of her marriage contract, in which this is included with many other appanages as her dower, dated Edinburgh, 6th May, 1503, 15th of James IV. Also to the same for her saisine,
'dominii de Strivelinshire,' William Edmonstone de Duntreath, captain of Doune, is witness among others. There is, moreover, an original infeftment, 20th January 1507, upon a royal precept of Archibald Napier of Monteith, in lands in Monteith, to which officially the seal of arms of William Edmonstone of Duntreath, as steward of Monteith, is appended. The arms are emblazoned with supporters and crest as now borne. Crauford, moreover, mentions a decreet, obtained at the instance of Sir James Haldane of Glenegles before William Edmonstone, as steward of Monteith.
He married first, Sibylla, daughter of Sir William Baillie of Lamington, an old and distinguished family now extinct. This marriage is attested by a charter in 1497 to William, son and heir of Archibald Edmonstone of Duntreath, and Sibylla Baillie, his wife, of the lands of Gartbarron; also by another charter to the same parties, of Argety and Rednock, dated 1506. Sir William's second wife was Elizabeth Leslie, daughter to George, first Earl of Rothes, who had been previously married to William, third Earl of Errol. This marriage took place probably about 1507 or 1508, but the lady did not very long survive, as there is an action before the Court of Session in 15 1 1, by William Edmonstone of Duntreath, as executor to 'Umquhile Dame Elizabeth Leslie, Countess of Errol', his spouse. Sir William married thirdly, as appears by a charter, in 1510, to William Edmonstone of
Duntreath, knight, and Katherine Forrest, his wife, of the lands of Glenboig and Cambusvvallace, but who this lady was I know not, as neither she nor the Countess of Errol are mentioned in Crauford's genealogy. Sir William married fourthly, Sibylla, daughter ofSir John Carmichael of that ilk, as is attested by a charter under the Great Seal, of the same lands of Glenboig and Cambusvvallace, to Sir William Edmonstone and Sibylla Carmichael, his wife, on his own resignation. It is dated August 15, 1513, and on the 9th of September he, together with his brothers-in-law, the Earl of Montrose and Lord Ross, fell at the fatal battle of Flodden.
It's not clear who the mother of his heir William was, though given that William the heir was of age by 1513 when is father died, it's most likely to have been
. Ref 1 below states that William (the son) is mentioned in a sasine dated 2
[1] Genealogical Account of The Family of Edmonstone, Archibald Edmonstone, 1875, pages 35 & 36
[2] See also Burke's Peerage (Edmonstone) which has some scant details on the early Edmonstones
Abt 1475 - 1513 (~ 38 years)
[1] 
