OK.
So this is the family in 1891:
RG12/2149 153 31
Newcastle under Lyme
Thomas Thorpe, head, 26, Pedlar, b. Rutland Uppingham
Margaret, wife, 21, b. Haslington Lancashire
James, son, 6 mo, b. Cheshire Crewe
Ellen White, mother in law, wid, 60, b. Lancashire Salford
Have you found a marriage for Margaret to David? Given I can't see one I was wondering if you knew for sure that they aren't one and the same man ... Have you identified both Thomas and David on a same census yet?