I have been researching Muzzlewhites for a friend who is the great grandchild of William Muzzlewhite (also spelt Muzzlewhit)William was born in 1876 in Tavistock and had a brother John who was born two years earlier. He may well be the John you have found but I am afraid I can find no other references to him either.
I am interested to know whether you have any information as to who his father was as Sarah is listed in the census for 1881 as the unmarried daughter of Maria Muzzlewhite and the two boys are there as "grandsons". ??? their father is unknown and they took their mothers sirname????

I do have some other information on William if you are interested.
many thanks
Rose