There's something quite odd about John Waddell. Quite apart from apparently marrying at 15.
The 1883 death in Glasgow states plainly that John was 'about 53 years' and that his parents were John Waddell and Janet Clelland.
The 1851 census lists, at 75 Whitevale Street, John Waddell, 25, carter, with wife Ratchel, 26, daughter Ratchel, 2 and son Mathew, aged 1 month, All born in Glasgow. The 1871 lists the now much larger family at 7 Burgher Street. John is 45, dairyman and Rachel 44, and five children. Again, all are listed as born in Glasgow. (A birth in 1825/6 gives a much more likely age at marriage of about 22.)
The problem arises because the 1851 census also lists at Chryston, Cadder a family consisting of John Waddell, 50, farmer; wife Janet, 45; John, 17; Grace, 14; William, 10; Janet, 7; Catherine, 5, all born in New Monkland. By 1861 John Sr has died, and the family consists of the widowed Janet, 54, with Grace, 23; William, 20; Janet, 18; and Catherine, 15. These children exactly match the children of John Waddell and Janet Cleland, apart from John's age; he would have been 18, not 17, on census day 1851.
So there are two John Waddells in the 1851 census: one born in Glasgow 1825/6 and married to Rachel Mackay, and one born in New Monkland, son of John Waddell and Janet Cleland, still living with his parents in Cadder.
So were there two couples, both named John Waddell and Janet Clel(l)and, one of whom had a son John in Glasgow in 1825/6, and the other of whom had a son John in New Monkland in 1832?
Or did John Waddell and Janet Cleland have a son John, born in Glasgow before their marriage, and a second son John, born in New Monkland after their marriage? And if so why was he not living with his parents and siblings in 1841?
Or did William Waddell, son of John Waddell and Rachel Mackay, give the wrong names for his grandparents when he registered his father's death, and if so why did he think they were John Waddell and Janet Clelland?
Or is there some other explanation?