Thank you for that information, Eric. It's good to eliminate possibilities.
I've been wondering whether Margaret Gill, mother of Elizabeth Sophia, was:
a) unmarried, and just coincidentally happened to have the same surname as the father of her child.
b) a widow, unrelated in any way to Robert Gill.
c) a widow, perhaps of a close relative of Robert Gill, eg possibly his sister in law.
Let's hope that the wills will prove to be illuminating.
Jean