Tradition says he married twice, but it is known that his second wife was Elizabeth McKie, probably daughter of Alexander McKie, a merchant of Kirkcudbright who disposed in 1685 to Alexander McKie Junior and Margaret Grierson his spouse, several tenements of Houses adjoining Castle Dykes.
Elizabeth's sister Margaret married John Halliday and had a son John who became a wealthy planter of Antigua. Margaret died in 1771, aged 88. From her union with John came Admiral Halliday who married Lady Jane Tollemache, whence the Tollemache-Hallidays. She was painted by Reynolds, her sister, Lady Louisa Manners, by Romney. Both are mentioned by Thomas Creedy, see the edition in 1 Vol. by John Gore, published in 1948, page 248.
"John Halliday", according to the Rt. Hon. William Lidderdale, writing to his cousin General Halliday, "returned to Galloway in 1757 on his father's death, on a visit, and went over to Ireland to see his aunt Elizabeth, Mrs. Robert Lidderdale. He brought back with him to Kirkcudbright his cousin William Lidderdale, intending to take him to Antigua to join the business. Mrs. Halliday, widow of John Halliday, took a great liking to her nephew, William Lidderdale, and persuaded him to stay at Kirkcudbright, where he became at first tenant, afterwards carrying on business with Ireland. It was believed by our family, of my uncles' generation, that the inducement held out to my grandfather to remain in Scotland was that the Castle Maines or Dykes property would be left to him at his aunt's death. Her son, John Halliday, was already rich. This proceeding was most unlucky for the Lidderdales. As a young man, Martin, who went out in place of my grandfather, made a fortune whilst the latter never did much for himself at home."
Margaret Halliday left all her goods and gear to him, making him her sole heir, universal legator and executor.
Source: Robert Halliday Lidderdale, An Account of the Lowland Scots Family of Lidderdale, 1950.