I think I have solved the puzzle- Cecil was in both WW1 and WW2 and the first two phages of his serviceon line refer to his enlistment 1940- he was a widower then- his wife died in 1939 and is buried at Fawlner Cemetery in Victoria with an infant son.
His date of birth in 1903 and aged 37 years would have been given to make himself appear younger than what he was.
Thus I do not think that there were any other previous marriages- there was a daughter born to them in 1920 as follows:
Spelling as per index record:
Surname: BYRNE Given Names: Emily Louise Event: B Sex: Spouse Surname/Father: Cecil Vincent Spouse Gvn Names/Mother: Emily GILES Age: Age Code: Birth Place: BRSWCK Death Place: Year: 1920 Reg. Number: 9732
He had two service numbers- one for WW1 and one for WW2:
This one is for WW2
Service Record Name BYRNE, CECIL VINCENT Service Australian Army Service Number VX31362 Date of Birth 3 Jun 1903 Place of Birth HOBART, TAS Date of Enlistment 11 Jun 1940 Locality on Enlistment BRUNSWICK, VIC Place of Enlistment ROYAL PARK, VIC Next of Kin BYRNE, MARIE Date of Discharge 11 Oct 1950 Rank Lance Corporal Posting at Discharge 2/22 Battalion WW2 Honours and Gallantry None for display Prisoner of War No