I also wonder why Francis Sabey named his first daughter Dinah.
Perhaps it was nothing more sinister than that they liked the name. Have you looked at his wife's side of the family to see it she had any Dinahs? Perhaps Charlotte's mother was Dinah.
What if
The second Peter son of Peter and Dinah Peter Saby bap 1735 at Roxton Beds married
Mary Hammett 1759 at Gt Stukeley, both otp. Mary was buried at Gt Stukeley on 11 Nov 1764 (no children found)
This is what I show in my tree with the warning that it's pure conjecture with not a shred of evidence. But there is another Sabey baptism in Gt Stukeley, on 4 Oct 1761 of John, son of Robert and Mary. There was only one Sabey family in Gt Stukeley at this time, Peter & Mary, and there's no trace of a Robert. I think Robert is a PR error, and it should be Peter, but that's unproveable.
Peter 1768 (?died 1839 Gt Stukeley married ?? a Francis Harden b abt 1777 (Ancestry Tree).
Unless the tree is mine I wouldn't place any credibility on Ancestry trees, and even if it were mine I'd still check it!
Could Frances born circa 1760-1766 have been born before the second marriage in 1766 which is why he was not baptised until his own marriage? Did Francis name his first daughter after his grandmother Dinah?
He could have been, but I don't think he was, and I don't follow the argument that the second marriage of his father was why his own baptism was delayed for 30 years.
Francis could have named his daughter after his grandmother I suppose, but it goes against naming patterns, where his own mother's name should have been used first, and is it really likely that he would have used the name of a grandmother who died 30 years before he was born?
I'm sorry but I'm still convinced that Francis was the non-conformist unbaptised son of the non-conformist Sabeys who were living in Bolnhurst at that time. To try to conjure up a scenario that he was the unbaptised son of Church of England parents living in Gt Stukeley, who baptised their other children, and that he then pitched up in Bolnhurst as a non-conformist, based solely on the speculation that he named a daughter Dinah after a grandmother who had died 30 years before he was born is too much for me. One can "what if" to the nth degree but there's not a shred of evidence to support it. If he'd been such a stickler for naming his children after his side of the family I'd have expected a son to be named Peter if Peter really was his own father.
There is also a Peter Seaby s of Thomas and Mary bap 1761 Harrold Beds who married Ann Errington in 1790 at Harold. Perhaps Peter's father was Tho Saby s of Peter and Dinah 1725 at Roxton Beds
Perhaps he was. Or perhaps he was from Northants.