| Place of birth | Sydney, New South Wales |
| School | St Ignatius College, Riverview, Sydney; Sydney Grammar School, New South Wales |
| Other training | University of Sydney, NSW |
| Religion | Roman Catholic |
| Occupation | Squatter |
| Address | Floradel, Edgecliff Road, Woollahra, New South Wales |
| Marital status | Single |
| Age at embarkation | 29 |
| Height | 5' 11.75" |
| Weight | 168 lbs |
| Next of kin | Father, William Francis Brennan, Floradel, Edgecliff Road, Woollahra, New South Wales |
| Previous military service | Nil |
| Enlistment date | |
| Place of enlistment | Liverpool, New South Wales |
| Rank on enlistment | 2nd Lieutenant |
| Unit name | 6th Light Horse Regiment, 13th Reinforcement |
| AWM Embarkation Roll number | 10/11/3 |
| Embarkation details | Unit embarked from Sydney, New South Wales, on board HMAT A60 Aeneas on |
| Fate | Died of wounds |
| Place of death or wounding | Gaza, Palestine |
| Age at death | 30 |
| Age at death from cemetery records | 30 |
| Place of burial | Gaza War Cemetery (Plot XX, Row D, grave No. 13), Palestine |
| Panel number, Roll of Honour, Australian War Memorial | 8 |
| Miscellaneous information from cemetery records | Parents: William Francis and Elizabeth BRENNAN, 375 George Street, Sydney, New South Wales |
| Family/military connections | Sister Adele BRENNAN, Voluntary Aid Detachment, died Leicester, England; Lieutenant John Clive BRENNAN, 4th Bn, wounded in France, returned to Australia, 20 June 1919. |
| Other details |
War service: Egypt, Palestine Taken on strength, 6th Light Horse Regiment, Maadi, 17 January 1916. Appointed Lieutenant, 22 February 1916. Transferred to 2nd Light Horse Reserve Regiment, 1 March 1916. Taken on strength, 12th Light Horse Regiment, 20 March 1916. Admitted to 1st Light Horse Field Ambulance, 24 May 1916 (inflamed eye); discharged to duty and rejoined unit, 26 May 1916. Marched out to Officers School of Instruction, Zeitoun, 31 December 1916; rejoined unit, 23 January 1917. Wounded in action, 19 April 1917; admitted to 4th Light Horse Field Ambulance Mobile Section, 19 April 1917 (gun shot wound, head and chest); transferred to Casualty Clearing Station, Tel-el-Jemmi, 20 April 1917; to 6th Mounted Brigade Field Ambulance, Tel-el-Jemmi, Palestine, 20 April 1917; died of wounds, 20 April 1917. Medals: British War Medal, Victory Medal British War Medal marked returned 19 August 1959 |
| Sources | NAA: B2455, BRENNAN William Keating |