He descended from a third son of Sir Andrew Kerr of Ferniehurst, and was laird of Ancrum in Roxburghshire. He was born about 1578, and succeeded to the family estate in 1590 on the death of his father, who was assassinated on the orders of his kinsman, Robert Ker, younger of Cessford. Cessford's men ambushed William Kerr of Ancram on the stairs at the entry to his lodging and shot him with a pistol called a "dag".
Robert Kerr was honoured at an early age with court favour. Soon after the king's accession to the English throne, Kerr occupied a considerable station in the household of Prince Henry. He joined the household of Prince Charles in 1613 as a gentleman of the bedchamber, gaining the position with the help of his cousin, the favourite Robert Carr, then Lord Rochester. Charles became his patron through life. Charles mediated the marriage between Sir Robert and the Lady Anne Stanley, daughter of the Earl of Derby.
In 1620, Kerr was involved in a fatal quarrel with Charles Maxwell, who insinuated that he had slighted the Duke of Buckingham and insulted him without provocation as he entered the palace at Newmarket. In a duel that followed, Sir Robert killed Maxwell. Even though Maxwell's friends acquitted Kerr of blame, the king's strict rules for prevention and punishment of duels forced him to flee to Holland, where he remained about a year. During his exile, he collected pictures, for which, like his royal master, he had good taste. He eventually presented those he brought back with him to the prince. He was also distinguished by his literary taste and was a friend of John Donne. He also lived in Whitehall Palace and Kew.
On 24 June 1633, when Charles was in Scotland at his coronation, Kerr was elevated to the peerage under the titles Earl of Ancram and Lord Kerr of Nisbet, Langnewton, and Dolphinstoun. Previously, his son William, by his first wife Elizabeth, daughter of Sir John Murray of Blackbarony, had married his relative, Anne, Countess of Lothian in her own right, and had been, by the king, given the title Earl of Lothian. It was therefore arranged, in the patent granted to Kerr, that his own title should descend to the children of his second marriage. Thus, he was father of two peers.
Unlike others who owed everything to this prince, the Earl of Ancram remained the prince's steady adherent during the whole of his troubles—though he was unable to prevent his eldest son, the Earl of Lothian, from acting a conspicuous part on the opposite side. On the death of King Charles, Kerr took refuge in Holland, where he spent the remainder of his days in solitary afflictions and poverty, and died in 1654, aged 76. Jan Lievens painted him marvelously.
He had two sons by his first marriage to Elizabeth Murray:
- Stanley Kerr (d. bef. May 1672)
- William Kerr, 1st Earl of Lothian(bef. 1615 – c. October 1675)
- Charles Kerr, 2nd Earl of Ancram (6 August 1624 – September 1690)
- Vere Kerr
- Elizabeth Kerr
This article incorporates text from a publication now in the public domain: "A biographical dictionary of eminent Scotsmen", Robert Chambers (1840)
- Jan Lievens portrait of Robert Kerr in the National Galleries of Scotland
- Chambers, Robert (1840), A biographical dictionary of eminent Scotsmen, Volume 3, Blackie and Son, pp 315-6.
- Henderson, Thomas Finlayson (1892). "Ker, Robert (1578-1654)". In Lee, Sidney (ed.). Dictionary of National Biography. 31. London: Smith, Elder & Co.
- Calendar State Papers Scotland, vol. 10 (Edinburgh, 1936), p. 430.
- Thomas Birch & Folkestone Williams, Court and Times of James the First, vol. 1 (London, 1848), p. 256.
- "KERR (CARR), Sir Robert (c.1578-1654), of Ancram, Roxburgh; Whitehall Palace and Kew, Surr. | History of Parliament Online". www.historyofparliamentonline.org. Retrieved 18 July 2021.
- David Laing, Correspondence of Sir Robert Kerr, first Earl of Ancram, vol. 1 (Edinburgh, 1875), p. xviii.
- David Laing, Correspondence of Sir Robert Kerr, first Earl of Ancram, vol. 1 (Edinburgh, 1875), pp. xlviii, li.