I'm not sure you're going to find a marriage for James Ramsay and Ann Low - or baptisms for their children - as it looks likely they weren't married.
This does appear to be them in 1851 in Dundee Road, Forfar:
James Ramsay, head, 50, handloom weaver, Dysart, Fife
Ann Ramsay, wife, 31, winder, Dysart, Fife
James Ramsay, son, 10, scholar, Dysart, Fife
Ann Ramsay, daughter, 6, scholar, Dysart, Fife
David Ramsay, son, 1, Forfar, Angus
I haven't had any luck tracking down a death for James Ramsay senior, Ann Low or James Ramsay junior. However, David Ramsay died aged 15 in 1866 in Alyth, Perthshire. On the death record he is described as illegitimate, with James Ramsay (deceased) being the 'reputed father' - the record was signed by Ann Low, mother.
Ruth