Braidwood - from Johnstone, Paisley, and surrounds c 19th century

[Willison]

Hi, I am hoping some insightful people can help me out here. (Especially anyone researching Braidwood (sometimes Broadwood) surname in Renfrewshire.
I have a couple in Paisley : Alexander Renfrew (1832-1910) and Ann Braidwood (1840-1888), married 1860, 2nd Feb at Johnstone, Renfrew. (559/3/9)
His parents are William Renfrew and Mary Braidwood (1808-1873), and hers as John Braidwood (1815-1866) and Isabella Husband. It stated below the bride's occupation "cousins" which fits with his mother and her father both having Braidwood as a surname. When loading my findings to a family tree in Ancestry it suggests potential parents for John Braidwood as being the same as those for Mary Renfrew, nee Braidwood (ie James Braidwood and Janet Hodgart), which seems feasible, and some other ancestry members seem to have followed that hint. However, I later found John Braidwood's death cert in 1866 (559/3 61) and it states his parents as Matthew Braidwood and Janet Hodgart.
The 1808 OPR for 559/Abbey page 381 of 593 states Janet Hodgart m. James "Broadwood" but I cannot find a marriage for a Matthew Braidwood and Janet Hodgart, or to anyone else for that matter. There seems to be precious little documentary evidence of Matthew Braidwood.
I am wondering if the original bride and groom mentioned above, Alexander Renfrew and Ann Braidwood, were second cousins and not "cousins", and that his mother and her father were cousins, not siblings, and it was the generation above them that contained Braidwood siblings.
But then there's the situation where Janet Hodgart apparently married and/or had children with James Braidwood and also Matthew Braidwood. I know that isn't impossible but I'm struggling to find the proof to work all this out.
I hope I have made things as clear as possible above, but I just can't make sense of a likely scenario.
I would appreciate any help and/or suggestions.
Many thanks in advance.

[WILLIAM 1]

i had one from 1820 the woman had a child then 1 year later she had another child. so the first child turned out her father was the child father . and her 2nd child was from someone else . so when both of her kids 1 was 16 the other 17 they married each other it was when she was dying she told everyone all about this. so both of her parents where dead at that time. so anyway i also have had that as well 2 couples members of my family male and female both had the same last names james burton & eileen burton / john burton & margaret burton