William Sydney Keegan was living with his mother, Margaret Keegan, in Princes St., Carlton, when he enlisted on 5 April, 1916. He was then 44 years and 6 months old, 5'5" tall, and working as a groom. In his later life, he did not marry, though he had a son, born in 1906, with Margaret Dunn, named Leslie Joseph Francis Hardy.

There is little to be found about him. There was a listing for a Keegan, no first name, born 1872, on the Index of State Wards (Victoria), but no date of further information. An 1891 Police Gazette wrote of a conviction for assault with intent to rob, to a William Keegan, b. 1872, labourer, which was probably him. He was given 9 months' gaol. In 1902, there was a conviction of horse stealing.

He was sent to the 10th Depot Battalion in Castlemaine, Victoria, from 13 March to 27 April, 1916, and was then placed with the 46th Battalion Reinforcements at Broadmeadows. He left for england on 4 May that year, on the H.M.A.T. Milliades. On 27 July, 1916, he marched in to Rolleston and was placed with the 12th Field Battery, embarking for France on 22 September, 1916.

On 21 October, William Keegan was sick at the battle front. He was sent to hospital, the 17th Casualty Clearing Station, 'in the field', and diagnosed with haemorrhoids. This ended his military career. He marched in to Etaples on 28 October, and was placed with the Australian Division Base there, awaiting return to Australia.

Two months later, he was sent back to England, marching out to Weymouth. and on 11 May, was sent back home, again on the Milliades, leaving from Devonport. The reason for discharge 'over age and haemorrhoids'. 

Attempts to find him post-war are difficult. In August, 1924, he wrote to Bse Records that his medals be sent to 142 Princes St., N. Carlton, presumably to his mother. He signed it and underneath wrote Kilifarra Station, -ivinhoe, NSW, the first letter of the town name being obscured. He is not on the Electoral Rolls until 1934, when he was working at Jerilderie as a labourer. In 1935, he was still a labourer, with his address The Yanko, Jerilderie. In 1936, he was living at the McConville Hotel at Narrandera, working as a groom. In 1937, he had moved to Gossold St., Wagga Wagga, again working as a groom. From there, he disappears from the Electoral Rolls. However, the death of a William Keegan in 1938 at Randwick, N.S.W. can be found in the Australian Deaths Index. He would have been 66 years old.