Alias (known by another name) was common, for whatever reason. I have HEWER alias RODBORN/RODBOURNE in my tree, which carried on for generations.

There are links by googling to explain the various reason. Trying to do the link..... but Google

Use of Aliases an Overview

https://www.familysearch.org/learn/wiki/en/Use_of_Aliases_-_an_Overview

From this site's FoD PRs I see the parents died young, sadly:

Record_ID: 303385
Entry_Number:
Year: 1844
Month: Mar
Day: 2
Surname: SMITH
Forenames: Benjamin
Residence: Beachley
Age_at_death: 35
Officiating_Minister:
Event: Burial
Cause_of_death:
Memoranda: alias COLLINS
Notes:
Register_Reference: BT
Page_No:
Parish_Chapel: Beachley
Soundex: S530

Record_ID: 303379
Entry_Number:
Year: 1841
Month: Aug
Day: 29
Surname: SMITH
Forenames: Mary
Residence: Beachley
Age_at_death: 45
Officiating_Minister:
Event: Burial
Cause_of_death:
Memoranda:
Notes:
Register_Reference: BT
Page_No:
Parish_Chapel: Beachley
Soundex: S530

Hence they will not be on the 1851 Glos Census.

Searching 1851 Glos Census for Henry Smith/Collins/Hyatt etc b1837
and William --//--//-- b1833
and Mary Anne --//--//-- b1835;

Here's William (and a Robert ??)

2443 1851 CENSUS HO107/2443 FF.0465-0481 ED.10B CHEPSTOW 2
Piece: 2443 Folio: 0472 Schedule: 031
Address: Beachley

REECE Matthew HD W 76 Shipwright MON Llantrissant (c1775)
SAUNDERS Thomas BL W 67 Fisherman GLS Tidenham (c1784)
SAUNDERS Thomas NP U 27 Fisherman MON Chepstow (c1824)
SAUNDERS Phillip NP U 20 Carpenter MON Chepstow (c1831)
DAVIS Mary SV U 29 House Serv MON Ragland [Raglan] (c1822)
TAYLER Noah VR U 65 Fisherman GLS Oldbury (c1786)
HIEET Robert LG U 26 Ag Lab GLS Tidenham (c1825)
SAUNDERS John NP U 35 Ag Lab GLS Bristol (c1816)
HIEET William LG U 17 Fisherman GLS Tidenham (c1834)

(BL = brother in law, NP = nephew, SV = servant, VR = visitor, LG = lodger)

------------------------------------------------------------------------------------

Mary Anne, as per MPG's post earlier:

2443 1851 CENSUS HO107/2443 FF.0593-0611 ED.4 LYDNEY 3
Piece: 2443 Folio: 0599 Schedule: 020
Address: Aylburton

YOUNG Andrew HD M 33 Carpenter GLS Tidenham (c1818)
YOUNG Eliza WI M 31 - GLS Tidenham (c1820)
YOUNG Esther DA - 6 - GLS Tidenham (c1845)
YOUNG Henry SO - 5 - GLS Tidenham (c1846)
YOUNG John SO - 1 - GLS Tidenham (c1850)
COLLINS Mary SV U 19 House Serv GLS Tidenham (c1832)
LANE Thomas LG U 30 Mason DEV - (c1821)
PHILLIPS John LG U 27 Butcher GLS Lydney (c1824)
JONES Joseph LG U 39 Forgman GLS Lydney (c1812)

-------------------------------------------------------------------------------------

SORRY, cannot find a Henry under any surname ! Perhaps he's out of the County ?

==============
LATER UPDATE !
==============
Re aforementioned Robert c1825, here he is in FoD PRs:

Record_ID: 61034
Entry_Number: 530
Year: 1829
Month: Sep
Day: 6
Parents_Surname: HIGHATT
Child_Forenames: Robert
Fathers_Forenames: James
Mothers_Forenames: Mary
Mothers_Surname:
Residence: Tidenham
Occupation: Labourer
Officiating_Minister: Tho[mas]Thomas
Event: Baptism
Memoranda:
Notes:
Register_Reference: P333/1 IN 1/3
Page_Number: 67
Parish_Chapel: Tidenham
Soundex: H230

I see there are other much earlier Severnside Roberts who may be ancestors, SEVERAL spelt Hyatt etc, but also see this odd spelling variation ?:

Record_ID: 186154
Entry_Number: 6
Year: 1768
Month: Mar
Day: 20
Parents_Surname: HIET
Child_Forenames: Robert
Fathers_Forenames: Daniel
Mothers_Forenames: Elizabeth
Mothers_Surname:
Residence:
Occupation:
Officiating_Minister:
Event: Baptism
Memoranda: S[on] of
Notes: Any abbreviated forenames have been expanded to the full name
Register_Reference: P209 IN 1/2
Page_Number: 33
Parish_Chapel: Lydney
Soundex: H300

Record_ID: 271245
Entry_Number:
Year: 1620
Month: Jun
Day: 5
Parents_Surname: HIET
Child_Forenames: Robert
Fathers_Forenames: William
Mothers_Forenames: [not stated]
Mothers_Surname:
Residence:
Occupation:
Officiating_Minister: [not stated]
Event: Baptism
Memoranda:
Notes:
Register_Reference: P83 IN 1/1
Page_Number: 39
Parish_Chapel: Churcham
Soundex: H300

SEARCH HINT for you Sandra:

I only found the above unexpected spelling variations while using the "%" wildcard character when typing the surname into the PR search page.

For example, just type "Hy%", this will find ALL the surnames starting "Hy....". Then repeat with "Hi%", then "Co%" for Collins etc. I think this is more reliable than relying on ticking the Soundex box. You can then quickly scan down the list of hits to pick out those most likely, eg Beachley area ones.

Good luck !