Hi Mark,
I have seen that burial of William in 1796. The only problem I have with that is that William would have been in his sixties by the time Jacob was born, so I'm not sure if that burial burial belongs to the father of Jacob.
I've only been able to find 2 other children of William and Martha nee Lewis myself, that is James 1787 and Elizabeth 1791. The only Richard I have found so far, is one baptised in 1788 to William and Mary Smith. Yes, I've also been informed about the Quaker connection too from a relative.
I think it's possible that Ann and Mary could have been the same person, unless Mary died and then William married a Ann Smith. Yes, the age does seem a little old in my opinion, so perhaps its a generation before?
What is the William Lifton you have found up north?
@Dudley, I haven't yet come across the names you've mentioned, but perhaps someone else may have done so.
Josh