Captain Alexander Dickson, died 1819

[trimochyn]

I'm trying to trace my 5th gf, Captain Alexander Dickson of the Royal Artillery. Here's what I know:

He married Janet Inglis, daughter of Dr William Inglis, surgeon of Edinburgh. They had one son, James, later a merchant in Edinburgh.
He died in 1819, in Peebles.
He was living in Kelso in 1786.

I have a settlement drawn up by William Inglis which confirms the marriage, son, and residence in Kelso, though weirdly William refers to his son-in-law as 'James.'

I also have a disposition drawn up by Alexander Dickson himself in 1781, in which he names his father-in-law William Inglis and, in the same sentence, 'James Dickson Esq late of Conheath Provost of Dumfries.'

I'm trying to figure out if Provost James Dickson - about whom there is some information - is Alexander Dickson's father, and if he isn't, who is? Dickson isn't an uncommon name in the Borders and I've found a lot of dead ends!

[trimochyn]

I've scraped together some more information and I think Captain Alexander is Provost John's son.

According to a pamphlet published in 1917 by the Niagara Historical Society, John Dickson of Conheath had four daughters and six sons, and it names the sons: Robert, William, John, Alexander, Thomas and Walter. William, Thomas and Robert went to Canada and did well (Robert married the daughter of a Sioux chief). Walter became a lawyer in Edinburgh and married a Goldie. I've also found three of the daughters. Here are the dates I know:

John James Dickson marries Helen Wight (1741-1784) in March 1758. Children:
Elizabeth, d. 1825
Margaret, d. 1827
Robert, 1768-1823
William, 1769-1846
Thomas, 1775-1825
Walter, 1776-1855

No birth date for Alexander, and nothing at all for John and one unnamed daughter.

My conjecture is that Alexander is the first child, born in or around 1759, which would allow him to reach a plausible age - just - to be a captain lieutenant in the Royal Artillery in 1777.

On the other hand, John James Dickson apparently had two brothers, Thomas and Nicholas, about whom I can find nothing. Alexander could be one of their sons, born slightly earlier...