I looked William Boyd up, and the War Graves Commission gave his age as 28. No 12215, died 02-09-1916
He had a grave ref.
There was another Wm James Boyd R.I.R., 15th Batt. No 12214, died 1-7-1916. He is on Theipval Memorial.
I suppose this is the same person.
You could try ordering a birth certificate for William Boyd,
father William, born circa 1888, but I suppose the surname and given names are fairly common.
If you are near a Mormon Family Hiistory Centre, you could look up the Irish birth indexes, and if there are more than one possible births, you can order photocopies from Dublin, this would be cheaper than paying for searches and official copies.
I think if you order an official copy, the fee covers a three year search in Dublin, or each Belfast GRO search covers five years.
Dublin Photocopies are 1euro 90, if you have the volume and page number, and a lot less than an official certificate.
Belfast does not do photocopies, and certificates are now £10 each, including search.
All the details are on the following Web Sites.www.groireland.ie
Dublin takes credit card orders on line. You can download application forms from both sites I think.