I had great difficulty in tracking their marriage, but was informed that there were registrations that had been locked away,
Pauline
Pauline may I ask who gave you this information please?I find the information that Henry lived 21 days a bit odd.
Where did that come from?
It is usual to list previous living children on birth certificates in Victoria.
It seems to me that you have read that on Thomas's birth certificate that Ellen is 2 years old and possibly if the birth registration was a number of days after the birth of Thomas and Henry, that the elder twin would be listed as XX number of days of age because he is previous issue to the younger twin. A bit difficult when the information on certificates is not detailed including column headings ... you have the advantage of having the certs and we do the guessing. All part of the challenge

There is no death registered for a Henry
ROBERTS in Victoria with parents Robert and Mary
CAULFIELD therefore I think you have misinterpreted the information on the birth certificate.
So there is no actual date for the marriage.
It is usual to have the date in full ie day, month and year. I doubt there was a marriage as there is definitely nothing for an Edward
ROBERTS to anyone in 1862. What were Edward and Mary's ages on the birth certs? Who was the informant?
I note there was a Mary
CAULFIELD in a spot of bother with her employer in 1862 in Ballarat.
Cheers
Cando