Just a thought - the arithmetic makes me wonder if there isn't a missing generation - or two! - in there. I seem to have in my tree a John Kneale who married a Mary Collister at the beginning of 1785 and had a son John Kneale at the end of it. In 1811 there is a John Kneale of the same parish marrying a Mary Collister! I like to think this is the son of the first John but I haven't proved it yet. Either way, these two couples could look like one in the baptism register. You wouldn't believe how often I've met this problem recently!