Hello Patrish,
MANY THANKS for your useful suggestions.
In answer to your questions :-
1) Haven't found any definite siblings so far.
2) The only witness on the Marriage bonds appears to be the bride's Father.
3) Out of 5 children found (and aside from Joseph & Anna Maria), I'm left with Joanna, Hannah, & Mary, in that order.
JOANNA being the firstborn could well be a clue.
However, the only Joanna Goddard I can find giving birth to children during the period 1738 -1770 in Wiltshire, is EDWARD GODDARD & JOANNA READ married 1754 and residing in Cliffe Pypard. They have a steady flow of 9 children 1755-1767, but no JOSEPH.
4) Joseph's age according to the Marriage Bond in 1784, is given as 38 (as you say, considerably older than the bride), but still status given as BACHELOR.
It's a bit of a mystery !
Thanks again for your help.
Kind regards, Alan.