Erica,
According to Stirnet, Sir Hew Dalrymple had two daughters named Marion. Both are listed as daughters of his first wife, Marion Hamilton. One of these two daughters is said to have married Sir Ludovick Grant of that Ilk, afterwards Sir Ludovick Colquhoun of Luss, and to have died on 17 January 1735.
https://www.stirnet.com/genie/data/british/dd/dalrymple03.php
It would appear to be the case, though, that Sir Ludovick Grant’s wife may have been Sir Hew’s daughter by his second marriage to Elizabeth Hamilton, although, presently I cannot be certain of this. See extracts below mentioned:
24 July 1713 x 1 September 1713: Nomination by Sir Hew Dalrymple of Northberwick, lord president of session, of dame Elizabeth Hamiltoun, his spouse, as tutorix and curatrix of Marion Dalrymple, their daughter, with consent of Sir David Dalrymple of Halls, bt., and others.
National Records of Scotland, Papers of the Hamilton-Dalrymple family of North Berwick, reference GD110/585
https://catalogue.nrscotland.gov.uk/nrsonlinecatalogue/details.aspx...
6 July 1727: Certificate signed by John Lamont, minister in Edinburgh of marriage of Lewis Colquhoun and Marion Dalrymple.
National Records of Scotland: Papers of the Ogilvy Family, Earls of Seafield, reference GD428/23/1
https://catalogue.nrscotland.gov.uk/nrsonlinecatalogue/details.aspx...
4 August 1727: Copy letter from James Grant of Grant and Sir Hew Dalrymple of North Berwick [about the] clandestine marriage of Ludovick Grant, the writer’s son, and Marion Dalrymple, recipient’s daughter.
https://catalogue.nrscotland.gov.uk/nrsonlinecatalogue/details.aspx...