The deceased's father, John Christian Monsen, was a miner and greengrocer at the Champion Gold Mine, Kookynie. He was born 6 December 1874 in Christchurch, New Zealand. He married Laura Tomsey Creech on 18 September 1899 at Menzies. She was born 26 June 1882 at Collingwood, Victoria. Of the six children known in the family, Eric was the youngest. His older siblings were: Dorothy Louise born circa 1900; John Kelvin born 1903 at Kookynie; Ronald Austin born 21 February 1905 at Kookynie; Beryl Olive born 16 October 1906; Allan Desmond born 23 June 1908 at Kookynie. Laura died 15 December 1945 in Perth.
On 16 July 1915, having been blighted by difficult financial circumstances for some time, John Christian Monsen enlisted, joining the 28th Battalion AIF. He left Australia for Egypt with the 6th reinforcements on the 2nd November, 1915 in the "HMAS Ulysses". Thrown into the Battle of the Somme, his military career was short-lived. He was wounded in action on the 3rd September 1916 at Mouquet Farm and transferred to the University War Hospital in Southampton. With a gunshot wound to his left leg, which was promptly amputated, and another gunshot wound to his left shoulder, John Monsen died of his wounds on the 15th September 1916 and was buried 18 September 1916 at the Military Cemetery Netley, England, Presbyterian site. Grave No 364.
Mary Louise Jessup (nee Power), was the mother of Laura Tomsey Creech and the grandmother of the deceased. In 1904, Mary Louise had a stillborn son, James Jessup, who is also buried in the Kookynie Cemetery.