Have you done these suggestions
write out a list of the children of the couple who married in Scotland in 1909.
The Irish did have a naming pattern and you can go through these and work out which family (husband or wife) may have contributed the names.
Checked Griffiths Valuation for mentions of Gallagher/Devlin
Checked the Irish Census for mentions of Devlin & Gallagher. While this part of the family may have moved to Scotland it does not mean all of them did. I usually search after switching to the age tab and look at the oldest ones first. If you have a list of what might be family names it is good to run through these
Even though you may feel the family came from Glenties, this might have been the nearest 'larger' town and they may have come from townlands on the outskirts
This site is worth having a poke around in
http://donegalgenealogy.com/Even though the name is Gallagher, not all the records may have this spelling. If the name is pronounced with a soft second G you might find records in the names Gallaher etc.
Find every Irish/general website you can and put in the names without limiting it to Donegal. Names and dates.
Family search
Ancestry
https://www.irishgenealogy.ie/en/RC Parish registers from PRONI
Start by extracting as much information as you can from the records you have
eg really interrogating the marriage certificate and death certificate for the 1909 people
Be aware also that if a person said they were of full age or that their parents had died this was not necessarily a fact. Under age marriages often had to get parental consent and sometimes it was easier to say that you were either of full age, even though you were not, or that both parents had died, even though they had not. I have found this happening on at least two other searches I have been involved with and found either
a) they were not of full age
b) the parent was still alive.
When recording from certificates you are certain of write down every name that appears so that means witnesses and those who report the death.
I usually keep these on spreadsheet called 'XXXXXX family mentions'
I record the names and where I got them from and periodically reorder the column headings
So the witnesses to the wedding may later be a sponsor/god parent to a child.
One of the key things is to put the names of all your key people into every register you come across. So Dog registers, reports of trials etc
Be aware that there was much movement between Donegal and Derry. So search in registers to do with both Counties.
Family Stories often contain a kernel/s of truth. Often though, like history being written by the winners, they can serve the interests of those telling the story. In my own family my gt grandfather was adamant he was the only child.....strange then to find a brother born to the same parents and bearing the unusual first name of one of my gt Uncles.
