[citation needed] He was the son and heir of John Stewart, 5th Seigneur d'Aubigny (d. 1567),[5] by his wife Anne de la Queuille, a French noblewoman.

On 5 August 1581, he was created Lord Aubigny, Dalkeith, Torboltoun and Aberdour, Earl of Darnley and Duke of Lennox, with a similar remainder,[6] as well as other favours.

[8] Esmé Stewart was potentially able to interest James in the Catholic religion and effect cultural change at court, controlling access to the king's bedchamber.

David Calderwood later alleged that Esmé Stewart had a fund or access to money which he used to reward and recruit allies, including Agnes Keith, Countess of Moray, but this seems doubtful.

For example, in July 1580 the English diplomat Robert Bowes reported that Lennox had obtained fishing rights in Aberdeen, which the deposed Regent Morton had given to his servant George Auchinleck of Balmanno, and had then arranged for the King to give this valuable source of income to the town.

In January 1582 she wrote from Sheffield to the French ambassador in London Michel de Castelnau, asking him to ensure Henry III of France supported Esmé and the restoration of the Auld Alliance.

Although the Scottish nobles believed that they would be proved right in their belief that Lennox's conversion was artificial following his return to France, he remained a Presbyterian.

[20] After Lennox's death William Schaw took his heart back to King James in Scotland, followed by his wife and eldest son Ludovic Stewart.

King James had repeatedly vouched for Lennox's religious sincerity and memorialized him in a poem called "Ane Tragedie of the Phoenix", which compared him to an exotic bird of unique beauty killed by envy.