Hello Val & Norma - welcome to RootsChat.... & hello David / Tazzie
OK I wish John had not been so clever to marry Mary - perhaps twice
The 26 July 1763 marriage does not offer more than their names - it does not state that John is a widower - but I suggest he was.
The 11 Oct 1749 marriage of John Clever to Mary Emerton says that they were both of Leighton Buzzard
John & Mary #1 baptised & buried a set of children between 1750 & 1760 that state John is a labourer; & then I find the burial of Mary wife of John Clever, labourer on 4 Nov 1760. Shortly after that 2 more burials in 1761 of Ellen & then Ann, daughters of John Clever. The burials all tie in with baptisms - if you want details let me know.
John & Mary #2 baptised & buried children between 1764 & 1777 repeating names of those who died in the previous partnership.
As to your question regarding the origins of John & Mary I have no idea.
regards John