Hello Stuart273,
You don't need to use Credits to do a Search on ScotlandsPeople.
Click on 1901 Census Records. Search for Surname: Henderson. Forename: Hary. County: Roxburgh. Distict: St Boswells. Age Range: 13 To 13 comes up with 1 match. No match for age 3 To 3.
Try each of the Henderson family forenames from the 1901 Census (Henry, Jessie, Andrew, Thomas, Jeannie) in the 'Second Person Forename' box. Each one comes up as a match with Hary age 13 To 13. No matches with Hary age 3 To 3.
Pretty sure this is the right family and that Hary is 13 not 3. Like you, I think he is the Henry age 3 on 1891 Census.
Scots named their children in a particular order, now referred to as the Scottish Naming Pattern.
1st son named after the father's father. 2nd son after the mother's father.
1st daughter after the mother's mother. 2nd daughter after the father's mother.
Although not all families followed this order, from the following Census Returns the Henderson male line appears to.
1851. Courthill, Berwickshire.
*Andrew Henderson 29 b Channelkirk, Berwick. * (Hary's Grandfather)
Jean " 28 b Eckford, Roxburgh.
**Henry " 3 b Smailholm, Roxburgh. **(Hary's father)
Betsy " 1 b " "
1861. Ancrum, Roxburgh.
*Andrew Henderson 39 b Channelkirk, Berwick.
Joan " 40 b Bedrule, Roxburgh.
**Henry " 13 b Smailholm, Roxburgh.
Elizabeth " 11 b " "
William 10, Alexander 8, John 5 & Robert Henderson 8months.
1871. Maxton, Roxburgh. (Littledean)
*Andrew Henderson 46 b Channelkirk, Berwick.
Joan " 48 b Cavers, Roxburgh.
Elizabeth 23, Robert 9 & George Henderson 8.
1871. Maxton, Roxburgh. (Hails Houses)
**Hendery Henderson 25 b Smailholm, Roxburgh.
Jessie " 20 b Wilton, "
Andrew " 2 b St Boswells, "
1881. St Boswells, Roxburgh.
**Hendry Henderson 35 b Smailholm, Roxburgh.
Jessie " 36 b Minto, "
Andrew " 12 b St Boswells "
Joan 6, Thomas 4 & Jane Henderson 1.
1891. St Boswells, Roxburgh.
**Henry Henderson 42 b Smailholm, Roxburgh.
Jessie " 42 b Minto, "
Andrew " 22 b St Boswells, "
Thomas " 14 b " "
Janie " 11 b " "
HENRY " 3 b " "
1901. St Boswells, Roxburgh.
**Henry Henderson 52 b Smailholm.
Jessie " 52 b Minto.
Andrew " 32 b St Boswells.
Thomas " 24 b "
Jeannie " 21 b "
HARY " 3? b "
Henry & Jessie's 1st son named Andrew after Henry's father.
Both Hary/Henry & brother Andrew name their 1st son Henry after their father Henry.
Your Henry/ Hary was probably known within the family as Harry to distinguish him from his father Henry. Wouldn't need an 'official' name change. I've found lots of name differences between baptism & marriage records in my own family. Jane/Jean, Isobel/Isabel/Isabella, Elisabeth/Elizabeth/Betsy etc. (See Monica's post re: name variants)
You mention a marriage at St Giles, Edinburgh with no witness names. Does it say "Warrant of the Sheriff" or something similar in the column the witnesses names usually appear in? (Ive found a couple of marriages at St Giles in my tree. Both were by Sheriff Warrant) If so, the witnesses names will be in the 1st column, titled When, Where & How Married. "By Declaration in the presence of.....(Witnesses names)".
Hope you manage to find Hary/Henry's DC. Good luck with your search.
Regards, Dod.