How Intriguing this is Liz!
Am I correct in my understanding that what your are reporting is the family I asked about are not named Vallis but actually Hiscox/Hiscock??
If so I have done some digging and have found that there is a reference to a Harry/Henry and his brother Charles Vallis b1862/1863 respectively whose mother is reported as a Martha Hiscox by a contemparary descendant (not verified).
With help from Forumites here is Harry/Henry at various times
1881 - Residence Higher Shepton, Shepton Montague, Somerset - with Charles
1891 - listed as FELIS - Residence Penmark, Glamorganshire
1901 - Residence Gilfach, Glamorganshire
1911 - Residence 6 John St, Bargoed, Glamorganshire
One of Harry's grandchildren is reported to have commented that before the brothers moved from Somerset to Wales their name was Hiscox!!
This would appear to be borne out by the 1871 entry of a Charles & Henry Hiscock - Residence Lower Shepton, Shepton Montague, Somerset
I also found a baptism of a Charles Vallis - 14-May-1874 Shepton Montague, Somerset
- parents reported as James Vallis & Martha Hiscock!
However I suspect that this is actually an adoption - as I noted that in the 1861 for a James & Louisa Vallis they have a Martha Hiscox, visitor, occupation servant also a Sarah Hiscox age 2. The name Hiscox is transcribed as Hixon.
in 1871 this same household in Lower Shepton, Shepton Montague, Somerset
is composed of:
James Vallis, age 54, Ag Lab b. Shepton Montague
Louisa Vallis, wife, age 56 b. Bruton, Somerset
Harry Hiscox, visitor, age 9 b. Shepton Montague
Charles Hiscox, visitor, age 7 b. Newport, Wales
HiFly