Hi
The Edward GANNON who married Catherine SIDDELL in 1914, has a WW1 Army Pension record:
Attested for Service: 4 Jul 1917: Edward GANNON age 24 & 8 mths, married.
Address: 3 Cross St, Liverpool,
Occupation: Baker
Corps: A.S.C Batl. (Baker), Reg. Nr: 358962
4' 11" tall
Next Of Kin: Catherine GANNON (wife) of 3 Cross Street, Liverpool
Particulars of Marriage:
Catherine SIDDELL (spinster) married 26 Sep 1914, West Derby
Children: (boy EJ as per FreeBMD) born 25 March 1915
His Birth date was given at one point in the record as: as 4 Sep 1892.
He was discharged (quite honourably) as Medically unfit to continue in Miitary Service.
Noting on FreeBMD he and Catherine had a 2nd child's birth registered Mar Qtr 1917 before he attested in Jul 1917, yet only the child born 1915 is accounted for on the form at both attestation and discharge time. A further check of the BMD's shows the 2nd son appears to have died shortly after he was born.
The stated dob (1892) and age in 1917, is a couple of years out on the date you have for your Edward, though.
Cheers
AMBLY