On the 1851 census, (transcribed as MUSHEL)

NEWLAND
High Nash

Robert MUSHET - 39, born Newland
Mary Ann MUSHET - 33 - St Briavels (nee THOMAS) - (married Cheltenham Dec qtr 1841)
Maxwell MUSHET - 8 - born Newland
Brooklyn MUSHET - age 5 - born Cheltenham
Lisowna? MUSHET - age 1 - born Cheltenham
Eliza THOMAS - age 25 c1826, Servant, born St Briavels
Emma WILLIAMS - age 22 - Servant - born Newland

Using the Advanced Search on FOD for births of THOMAS (Father John - didn't put the mother's christian name in the search box) - in St Briavels - sometimes the mother is called Catherine/Catharina/Christian - and on the 1841 census, Caroline - and children of the same family are both baptised on the same day - so difficult to pin-point the correct age of the child.

?

Mary THOMAS - christened at St Briavels - 23 August 1818 John & Catherina along with brother Thomas

Eliza THOMAS - christened 6 September 1829, John & Catharine

Lots of children including

Decima THOMAS - christened 21 February 1836, St Briavels, parents John & Christian

1841 census St Briavels

THOMAS

John - 60 - Farmer
Caroline - 50
William - 15 - 9 December 1821, John & Catherine) ****
1871 Census, age 50 with Daniel CROOME - transcribed as Daniel CROOMS & Catherine Lizze CROOMS
Alice - 18 - 29 June 1823, John & Catherine
John - 14 - 12 March 1826, John & Christian
George - 10
Eliza - 12
Decemia - 5

1851 Census, St Briavels

THOMAS

John -79, Farmer, born Woolaston
Catharine - 63, born Monmouthshire, Trelleck
William - 28, Farmer's Son, born St Briavels
John - 26, ditto
George - 19 - Carpenter
Decima - 15

1861 Census St Briavels

John THOMAS - age 87, Farmer, born woolaston
Catharine THOMAS - age 71 - born Trelleck
William THOMAS - unmarried, age 40, born St Briavels (assume he went to live with his sister and her husband after the death of his parents?)