There were 6 Robert Bryden/Brydon’s born in Scotland 1768-1783, two in Dumfriesshire, which may not help.
BRYDEN ROBERT JOHN BRYDEN/ELIZABETH CORRIE 05/05/1776 Lochmaben
BRYDEN ROBERT JOHN BRYDEN/JANET CORRIE 21/03/1777 Kirkmichael
In the same period 164 Agnes Smith's in Scotland, 14 in Dumfriesshire, one in Kirkmichael and three in Lochmaben
No marriages for Robert & Agnes on SP
Children of ROBERT BRYDEN/AGNES SMITH
Kirkmichael
WILLIAM 15/12/1799, JOHN 8/11/1801, JANET 14/05/1803
Tinwald
MARYANN 1/04/1805, JEAN11/01/1809, JAMES SMITH 28/12/1810, JAMES 16/06/1813
Morton
WILLIAM 12/08/1800 – so if there were two Robert & Agnes marriages maybe this is the odd one out?
The following census on freecen, no record for the Janet & Thomas mentioned?
1841 - Trailflatt Village, Tinwald
BRYDEN Robert M 65 Labourer Bleacher DFS
SMITH Agnes F 60 DFS
BRYDEN Janet F 25 DFS
BRYDEN Thomas M 20 Mason DFS
BRYDEN James M 18 Mason DFS
Colin