This is where the headache starts :-

Year: 1836
Month: Jul
Day: 12
Surname: TRIGG
Forenames: Benjamin
Residence: Drybrook
Age_at_death: 47 years
Officiating_Minister: H.Berkin
Event: Burial
Cause_of_death:
Memoranda:
Notes:
Register_Reference: P109 IN 1/11
Page_No: 42
Parish_Chapel: Drybrook

with the MARFELL connection that you mention Jim A is the "expert" to advise.

Instinct ( to me) tends to support the 1791 Benjamin - but that is not the proof you are looking for
Year: 1791
Month: Aug
Day: 28
Parents_Surname: TRIGG
Child_Forenames: Benjamin
Fathers_Forenames: Benjamin
Mothers_Forenames: Priscilla

<< <<< <<<

Year: 1813
Month: Sep
Day: 20
Grooms_Surname: TRIGG
Grooms_Forenames: Benjamin
Grooms_Age: [not stated]
Groom_Condition: [not stated]
Grooms_Occupation: [not stated]
Grooms_Residence: extraparochial land adjoining this parish
Grooms_Fathers_Surname: [not stated]
Grooms_Fathers_Forenames: [not stated]
Grooms_Fathers_Occupation: [not stated]
Brides_Surname: ROBERTS
Brides_Forenames: Elizabeth
Brides_Age: [not stated]
Brides_Condition: [not stated]
Brides_Occupation: [not stated]
Brides_Residence: extraparochial land adjoining this parish
Brides_Fathers_Surname: [not stated]
Brides_Fathers_Forenames: [not stated]
Brides_Fathers_Occupation: [not stated]
Licence_or_Banns: Banns
Date_of_Banns: 1813 Sep 5 12 19
Signature_or_Mark: Both mark
Witness_1: Mark of James Griffiths
Witness_2: Hannah Meek
Other_Witnesses:
Officiating_Minister: John Seager Curate
Event: Marriage
Memoranda: With consent of Parents
Notes: Banns are in P138 IN 1/7 page 114
Register_Reference: P138 IN 1/8
Page_Number: 4
Parish_Chapel: English Bicknor

Year: 1829
Month: Jan
Day: 25
Parents_Surname: TRIGG
Child_Forenames: Edwin
Fathers_Forenames: Benjamin
Mothers_Forenames: Elizabeth
Mothers_Surname:
Residence: Drybrook
Occupation: Quarryman
Officiating_Minister: J. Chell
Event: Baptism
Memoranda:
Notes:
Register_Reference: P109 IN 1/1
Page_Number: 88
Parish_Chapel: Drybrook

Year: 1831
Month: Aug
Day: 7
Parents_Surname: TRIGG
Child_Forenames: Absalom
Fathers_Forenames: Benjamin
Mothers_Forenames: Elizabeth
Mothers_Surname:
Residence: Drybrook
Occupation: Quarryman
Officiating_Minister: H. Berkin
Event: Baptism
Memoranda:
Notes:
Register_Reference: P109 IN 1/1
Page_Number: 113
Parish_Chapel: Drybrook

1841Haseley
Benjamin Trigg abt 1823 Gloucestershire, England Dean Forest, Gloucestershire
Edwin Trigg abt 1830 Gloucestershire, England Dean Forest, Gloucestershire
Absolam Trigg abt 1833 Gloucestershire, England Dean Forest, Gloucestershire

1851 Census
GLOVER John 45 Coal Miner Westbury on Severn
Elizabeth 55 Dean Forest
Edwin Stepson 22 Coal Miner Ruardean
Absolom Stepson 18 Coal Miner Ruardean
GLOVER George 11 Scholar Ruardean

1861Census
John Glover abt 1813 Little Dean Head
Elizabeth Glover abt 1796 East DeanWife
George Glover abt 1839 East Dean Son
Absalom Trigg abt 1835 East Dean Stepson

--
Ἀριστοτέλης A Gloster & Hereford Boy in the Forest of Dean ><((((*>

As Slowhands has mentioned, I have an interest here. I have actually changed my tree relating to the Benjamin Triggs based upon other researchers information. It is however difficult to be absolutely 100% positive. I have a copy of the will for John Marfell, father of the Mary Marfell who married "Benjamin Trigg", but whilst it fits exactly the details of Mary Marfells siblings from both John Marfells marriages to Sarah Bevan & Elizabeth Roberts (born 1769 - daughter of John Drinkwater Roberts)and whilst mentioning Benjamin Trigg, it does not conclusively identify which "Benjamin Trigg". I have copied it below my reply to this question:

My "version" I believe coincides with Slowhands thoughts. As above I cannot be 100% sure:

Benjamin Trigg baptised 30 Sep 1787 was the son of Richard Trigg & Elizabeth Jenkins. He married Mary Marfell.

Benjamin Trigg baptised 28 Aug 1791 was the son of Benjamin Trigg & Priscilla Welsh. He married Elizabeth Roberts (born 1795 - daughter of Moses Roberts) 20 Sep 1813 and on his death Jul 1836, she married John Glover 14 Jan 1837. The Trigg children subsequently appear with John Glover :

1851 Census
GLOVER John 45 Coal Miner Westbury on Severn
Elizabeth 55 Dean Forest
Edwin Stepson 22 Coal Miner Ruardean
Absolom Stepson 18 Coal Miner Ruardean
GLOVER George 11 Scholar Ruardean

1861Census
Elizabeth Glover abt 1796 East DeanWife
George Glover abt 1839 East Dean Son
John Glover abt 1813 Little Dean Head
Absalom Trigg abt 1835 East Dean Stepson

Jim Ashton

John Marfell Will. Note Aaron Marfell was from second marriage to Sarah Bevan :

John MARFELL dated 12th February 1841
Aaron MARFELL of Drybrook appeared personally- Will of John MARFELL late of Drybrook dated 18th July 1840...declared given into the custody of...

...last Will and Testament of me John MARFELL of Drybrook...farmer...I give...unto my son Aaron MARFELL all that my farm lands and premises situate at the Morse in the parish of Ruardean...which I sometime since purchased of Kingsmill Evans Esquire Lord of the Manor of Ruardean aforesaid part of whereof is now in my own occupation and the remainder is held by Mary ROBERTS widow for the remained of the lease granted previously to my purchasing the same which lease will expire on the 2nd February 1848 to hold the same...unto my said son Aaron MARFELL his heirs...for ever subject nevertheless and charged and chargeable with the payment of the sum of 100 pounds unto my son-in-law Benjamin TRIGG his executors...at the expiration of twelve calandar months next after my decease in case I shall survive the expiration of the lease so as aforesaid granted to the said Mary ROBERTS and in case I shall die before the expiration of the said leave then I direct the same to be paid unto my said son-in-law Benjamin TRIGG his executors...at the expiration of twelve calendar months from the termination of such lease and also...the sum of 20 pounds to each of my grandsons John TRIGG, son of my daughter Lucy decreased and George and William MARFELL( sons of my son Absalom decreased )...20 pounds to each of my grandsons John TRIGG, son of my daughter Lucy deceased and George and William MARFELL( sons of my son Absalom deceased )...20 pounds to John TRIGG on the 2nd Februarty 1850 and the other...on the 2nd February 1853...20 pounds to grandson George MARFELL on the 2nd February 1851 and in case I shall survive the expiration of such a lease then I will and direct that such legacies shall be payable at the like periods of time calculated from my decease as though I had died previous to the expiration of the said lease...I give unto my said son Aaron MARFELL one equal half part...of my piece of land called Bevans patch situate near Lockyers Farm...and now in my own occupation to hold unto my said son Aaron, his heirs...and ...the other half part...I give unto my daughter Elizabeth, the wife of James MATTHEWS,...during her natural life and after her decease, I give and devise the same unto her two daughters Sarah Jane and Eliza and their heirs...I give and devise all that piece of land called Prossers Patch situate on Harry Hill in the said Forest of Dean unto my said son-in-law James MATTHEWS and my daughter Elizabeth for and during thier natural life and the life of the survivor of them and from and after the decease of such survivor I give and devise the same unto thier said two children Sarah Jane and Eliza...and all the rest of my real and personal estate...I give..unto my said son Aaron MARFELL his heirs...and appoint my said son Aaron sole executor of this my Will...

Signed by J MARFELL 18th July 1840

Thank you both, Jim and Slowhands. I have spent a few hours toing and froing after your replies. They were a great help.
My reasoning is this:
The Benjamin Trigg who married Mary Marfell was still alive in 1841 (the date of the will).
One of the witnesses to the marriage of Benjamin and Mary was Sarah Trigg.
There is no Sarah Trigg in my Benjamin's family - but Benjamin (son of Richard & Elizabeth) had a sister, Sarah.
(Grief! I was getting confused there for a bit!)
I am going to use this as my basis that my Benjamin Trigg was the son of Benjamin and Priscilla.
It's the only logical answer, although as you say, no definitive proof.

Thank you both for your help
All the best