I have had another look at the census information for Leeds in 1851. I'm going to ignore for this discussion the 66-year-old Robert Maud who was living with his wife and Margaret and son Samuel in Escott township, although that must surely complicate things.
So, there is Henry (45) living with his wife Hannah and family in the vicinity of C8 L17 in Elizabethtown twp. Living with them was Robert Maud (84). No relationships are given in the census.
Then, not far away in Landsdown twp., there is the family of Robert (63) and Ann Maud (42).
Since we know from Henry's marriage record (2nd marriage?) from 1858 that his parents were named Robert and Ann.
Have you considered that the 84-year-old Robert might have been Henry's grand-father not his father?