Yes, sorry, I see you said that (it's been a long day!) Unfortunately not an uncommon forename... I had hoped the combination of several siblings might lead to a common set of births.
What don't you understand about it? People in the army did not spend the entire time away. My own great grandfather was fighting in France in WW1, came back (presumably on leave), got married and then was shipped back out again. Things like that did happen.
I would suggest that the marriage cert, if you know the details (buy direct from GRO not Ancestry though), would be the way to go for his parentage. The death certificate, if it is his, would I believe have his place of birth as well as the date- hopefully other details will tie in, such as the manner of his death, his occupation, and the informant provided it wasn't delivered by the coroner instead.