Martin Bligh Sr seems to have signed up for WWI - registered under Blyth, signed up in 1918. (Available on NAA Search). Next of kin his a sister, Mrs Doreen Anderson (Doreen Bligh m. Jack Anderson, 1913). Within the records is a letter mentioning that he'd tried to join the army earlier but had been rejected as at the time they were not allowing "half-castes" to join.
You may find more info on him and the rest of the family if you also look under Blyth/Blythe.
http://trove.nla.gov.au/ndp/del/article/48047249?searchTerm=%22Martin%20Blyth%22&searchLimits= - at least somebody had his back!
