Is this your Duncan in 1841 at Dalfield Walk, Dundee: gardener, aged 50, with Janet, 45; Jess, 20; David, 15; Margret, 15; Christina, 13; Grace, 11, and Mary, 4?
Colin is already married and with his wife and baby in Inchture.
Mary McLaren, age 9, daughter of Duncan McLaren, labourer was buried in the Howff, Dundee, on 28 August 1846.
Duncan McLaren, 68, was buried in the New Howff on 17 February 1855. The death certificate of Duncan McLaren who died on 14 February 1855 is all but illegible, and is indexed as age 18, so one or the other must be wrong. He died in the Asylum, so there is a possibility that there might be information about him in the asylum records. See
https://www.dundee.ac.uk/archives/thecollections/ NHS Tayside Archive.