Alfred James Smith II
The uniforms in the photograph are defiantly Merchant Navy, or more correctly Mercantile Marine. It is not clear but I think his sleeve insignia would indicate a Wireless officer. Others with better eyes may be able to advise you.
There were several ships named MILTIADES and some of them made voyages to Australia.
An educated guess is the MILTIADES official number 118179, 6,793 tons built in 1903 and owned by G W Thompson(Aberdeen Line)
She has several Crew Agreements From 1903 until she had a change of name in 1921. Most of these are stored in Newfoundland and are not available to view online.
http://www.mun.ca/mha/holdings/viewcombinedcrews.php?Official_No=118179The others for the remaining years are in the British National Archive and for years end in "5" National Maritime Museum, Greenwich. Likewise these cannot be viewed online. Ships crew agreements are indexed via Official Number. Searching the crew agreements should give you a lot of information about him, Age, NOK, last address etc and importantly his Certificate number or discharge number.
Lieutenant, was not a Mercantile Marine rank. It was a Royal Navy rank. It could be he served in the RNVR or RNR.
I found this one in the RNVR records
http://www.nationalarchives.gov.uk/documentsonline/details-result.asp?Edoc_Id=8038248&queryType=1&resultcount=19It may pay you to download it.
For details of MILTIADES just type Miltiades Aberdeen into Google but beware of other ships bearing the same name.