About Alexander de Wyntoun of Seton
Alan de Winton assumed his wife's name, and died in the Holy Land, leaving besides a daughter Christian de Seton who became Countess of Dunbar and March, three sons:
1st Sir William Seton, his successor and 1st Lord Seton;
2nd Alexander Seton who married Jean Halyburton, daughter of Sir Thomas Halyburton of Dirleton (recorded by Alexander Nisbet);
3rd Henry who retained his father's name and inherited Wrychthouses (Wrightshouses, Edinburgh). One of the oldest stones of this mansion bears the Seton's arms.
http://www2.thesetonfamily.com:8080/information/The_Setons_of_Scotland_044-110.pdf Page-45 at the very Bottom
In an account of the Seton family compiled by Alexander Nisbet the well known writer on Heraldrv a fifth Sir Alexander Seton is set down and it is stated that he married Jean daughter to Sir Thomas Halyburton of Dirleton but he may have been only a collateral of certain but undetermined degree of kinship Nisbet saw the Seton and Halyburton arms impaled as baron and femme on "an old genealogical tree" in the possession of the Earl of Winton at Seton House