Jonas Zeleniakas was born in Panemunė, Lithuania, but grew up in England. The family returned to Lithuania before the First World War and settled in Šančiai, a suburb of Kaunas. He had two sisters and two brothers, Antanas and Karolis. After the declaration of Lithuanian independence in 1918, Jonas was one of the first to volunteer and join the new Lithuanian army which was trying to defend the new national borders (in the Lithuanian language he was a Lietuvos Kariuomenės Kurėjas Savanoris). His brother Antanas also joined the army and rose to officer rank, however he died during the Second World War.
By the mid 1920s Jonas had decided to try his luck elsewhere; he left London aboard the Orvieto on 31 August 1929 bound for Australia. Almost immediately after arriving, in October 1929, he was elected to the founding committee of the Australian Lithuanian Society. Initially he lived in Sydney, but later settled at Port Kembla where he worked in a steel mill with the intention of saving enough to buy a house and bring a bride out from Lithuania. Unfortunately the Second World War interrupted those plans and he remained a bachelor for the rest of his life.
In October 1939, after 10 years residence in Australia, Jonas published a notice of his intention to take out Australian citizenship. He gave his place of residence as Perkins Beach, Port Kembla.
After WW2 his brother Karolis, who had escaped the soviet occupation, came out to Australia with his family. Karolis had been born in 1901 in England, his wife Marija in Kaunas, and their son Algirdas in 1928 in Kaunas. The Australian press reported in 1949 that both Karolis and Algirdas were commercial photographers who hoped to open a studio in Sydney; however by the mid-1950s Karolis and his family had moved to the USA.
When Jonas retired from the steel mill he bought a motor boat; he enjoyed fishing in the Pacific ocean and many Lithuanians would come down from Sydney to go fishing with him. He died at Port Kembla on 8 June 1975 and was buried at the West Dapto Catholic cemetery. A cemetery record at http://www.interment.net/data/aus/nsw/southcoastillawarra/wdcatholic/catholic.htm shows he also used the name 'John Green' in Australia (seemingly an appropriate play on words for him as the Lithuanian surname Zeleniakas - while having no specific association in that language - was likely derived from Polish, where the word for green is zielony).
Much of the above material is from the obituary for Jonas Zeleniakas written by Antanas Baužė and published in Mūsų Pastogė, Nr. 24 of 23rd June 1975.