The Countess of Dalkeith [nee Elizabeth Honor Cobbe, born 1986], wife of Walter John Francis Scott, formerly Montagu Douglas Scott, styled Earl of Dalkeith (b 8 Aug, 1984), gave birth to a son, and heir, Willoughby Ralph, styled Viscount of Nith, in 2016, twin with a sister, Lady Hester Florence.
Lord Dalkeith is the elder son and heir of the 10th Duke of Buccleuch & Queensberry, KBE, DL (b 1954), by his wife the former Lady Elizabeth Marian Frances Kerr (b 1954), scion of the Marquesses of Lothian,
Lady Dalkeith is a sion of that Irish gentry family of Newbridge House, Dublinounger younger daughter of Mr Hugh Michael Thomas Cobbe (b 1942), of East Woodhay, Hampshire, by his wife the former Katherine Elizabeth Chichester, dau of Charles Chichester.
The Cobbe forebears include Frankland baronets, Arbuthnots and John Jay (1745-1829), one of the most important of the American Founding Fathers -- co-author of the "Federalist Papers" and first chief justice of the United States.
The infant will use as a courtesy title one of the many peerages of his grandfather. They include that of the Viscount of Nith, Tortholwald and Ross, Lord Scott of Buccleuch, Lord Scott of Whitchester and Eskdaill, Baron Scott of Tindale, or Lord Douglas of Kilmount, Middlebie and Dornock.
It is likely that the Lordship of Eskdaill will be used.