Many thanks for the reply. I'll check out the link you so kindly provided, although I'm not sure I could afford a DNA test as I'm an OAP.
I'll also try to find the Kirk session records to see if they contain anything useful. And, I'll take a look at the other possibilities you mention, as well as, maybe, asking the Huntingdon parish records - again if I can afford their fee.
It gets so frustrating when you hit a brick wall.