According to FreeCen there is the following family at High Street, Blairgowrie, Perthshire in 1851
James Stewart, 49, Butcher born Blair Atholl
Catherine Stewart, 39, wife born Blair Atholl
But I get the feeling this isn't the family as there are 7 children living here; Elizabeth, Alexander, William, Margaret, Ann, James and Peter all born Blair Atholl.
Is it possible the occupation on William's marriage certificate says Slater rather than Flesher? Could he have changed occupation, and lastly, could the family/parents have emigrated between 1841 and 1851?
EDIT; though do remember that census info isn't infallible and I've seen wrong info like this before.