I was thinking first son, John Hastings, caught both grandfathers: John Abercrombie & the Dial one. But! Martin is said to be son of Henry Arthur Dial! Do we have the correct parentage for Martin? Do we even have a correct birthdate for Martin? Was it 30 Dec 1744, or was it 30 Dec 1749, or was it even later (making him the son of Hastings, not Henry Arthur)?
Given Hastings Dial's birthdate of 1732, it's entirely possible he had a wife & children prior to his marriage to Rebecca Abercrombie. I note that Martin is not a common Dial given name, except in the Martin Dial/Chrystie Abercrombie line.
Am still interested in hearing more on your Colvill Abercrombie theory -- his wife's name & their children.