Hi Kate, and welcome to RootsChat.
I'm afraid I am a wee bit confused by what you have written, but I'm sure we can help.
Presumably you have the marriage certificate of John Morrison and Janet Paton. What was William Morrison's occupation? And what,
exactly, was his mother's surname listed as? Where was he residing?
Do you have any actual birth, marriage and death certificates or original census records for any other of these folk? You can get these from
www.scotlandspeople.gov.uk (SP) at modest cost. You will need these to be sure of anything but we can probably find out quite a bit from other sources.
I see from
http://libindx.moray.gov.uk/mainmenu.asp that John Morrison also ran the Plough Inn in Keith for a few years before he died and that his age at death was given as 60. The index at
www.scotlandspeople.gov.uk (SP) tells me that Jessie Paton or Morrison died in Botriphnie in 1891 aged 42. (Drummuir is in the parish of Botriphnie.)
The 1881 census lists at Eastertown, Botriphnie John Morrison, 34, gamekeeper, born Boyndie; wife Jessie, 30, born Peterhead; daughter Jessie Ann, 1, born Forglen, and a lodger. (The names Janet and Jessie are used interchangeably in Scotland.)
Unfortunately Scotland's People lists only one baptism of a John Mor(r)ison in Boyndie in the 1840s, the son of John Morrison and Isabella Sievwright, baptised in 1846, who is obviously not yours.
According to the transcriptions at
https://www.freecen.org.uk/cgi/search.pl there are two John Morrisons, both born in Boyndie, both farm servants in King Edward in 1871. One is 25 and the other 27. The 25-year-old is at Balchers, but he could be the one I just mentioned above. He is just one of several servants in the household, and it is most likely just coincidence that the farmer's aunt's surname is the same.
In 1861 there is just one, a 16-year-old John Morison, born Boyndie, a cattleman at Little Crannah, Marnoch. He is the only John Mor(r)ison born in Boyndie in the 1840s in the FreeCEN transcription of the 1861 census.
In 1851 John Morison, aged 5, born Boyndie, is described as 'wife's son' in the census at Pitgair, Gamrie. The head of the household is James Birnie, farmer, 40, born Tyrie and the wife is Isabella Birnie, 33, born Boyndie. James Birnie married Isabella Sievwright in Gamrie in 1850. So this one isn't yours, and it looks as if yours isn't in any census before (possibly) 1871. He is the only John Mor(r)ison born in Boyndie in the 1840s in the FreeCEN transcription of the 1851 census, and the only John Mor(r)ison aged 4 to 8 living in Banffshire in a household with an Isabella in the SP index to the 1851 census.
Therefore the probability is that your John Morrison was illegitimate, which will make it much harder to find out who his father was.