Sir Alexander Seton was the second son of George, 3rd Earl of Winton by his 1st wife Anne Hay. Born 13 March 1620, knighted early in life, he was well educated and pursued a military career.  With his father he was highly active in the support of the Stuart Monarchy and of King Charles II.  A Captain of the Royalist forces, he was commander of Tantallon Castle and was responsible for the famous raids against Cromwell with his moss-troopers based in Tantallon.  In 1650 Cromwell's forces were busily conquering Scotland when Tantallon was occupied by this small group of moss-troopers and headed by Captain Seton they set to work attacking Cromwell's lines of communication across south east Scotland and were said to be more effective than all the regular troops opposing Cromwell across Scotland combined. Retaliation followed in 1651 and General Monk with a force of 3000 was ordered to attack the castle using much of Cromwell's artillery in Scotland, which was needed to root out a garrison of fewer than 100. For 12 days the English guns bombarded Tantallon when they finally breached the castle walls and overcame Captain Seton and his men, and the garrison surrendered.

A shortened simplified translation reads:  '....Captain Alexander Seton defended the same gallantly; but after the enemy cannon had opened a very large breach, and filled the dry ditch with the wall, he entered it by storm. The Captain and these few men (which) were with him, betook themselves to (the) tower, and resolved to sell their lives as good as they could, if quarter should (be) denayed them; but the enemy seeing them stand gallantly to it, prefered them quarters, which they excepted.' 

Viscount Kingston was married 4 times: 1st to Jean Fletcher (dau of Sir George Fletcher), 2nd to (c1661) Elizabeth Douglas (b c1636, d 1668, dau of Sir Archibald Douglas of Whittinghame and who brought the estates of Whittingehame and Stoneypath); 3rd to Elizabeth Hamilton (dau of John Hamilton, 1st Lord Belhaven) and 4th to (03/4.08.1686) Margaret Douglas (b 09.1651, d 10.1699/12.10.1692, dau of Archibald, Earl of Angus).

On the death of the 4th Earl of Winton, Archibald, 2nd Viscount of Kingston, the next heir, taking for granted that the young 5th Earl was dead, was proceeding to take possession of the title and estates of the Head of the Seton Family, when the 5th Earl suddenly appeared and vindicated his rights.