Siblings for William in Great Ellingham Ann, Mary and John.
Siblings in Elsing Alice (Hardi), Anne, Thomas, James, Robert, John, Matthew, Elizabeth, Thomasine. So no real clues there.
I would usually look at both families and follow some of the children, did they all stay in the parish or did they move around. Are any of your Hardy family clerks? Also William & Ann and John & Thomasine, who were their parents, might be a clue in the names somewhere.
Shirl