I have a brick wall I'd love to even crack a little please

I'm posting on the Australian board as that's where they lived, though I have no idea where this couple originated. I cannot find an Australian marriage (or arrival).
Here's what I know:
Joseph HUNTER born c1864, involved in tin mining in Western Australia, where he died in 1922, aged 58 (buried Bunbury). He went bankrupt in 1911, having been in the state of WA for 17 years. Prior to this I know he was in Qld, where he had a daughter. I have his obit from Trove.
His wife was
Mary DEVLIN (could it be D'EVLIN?) who died 1931 aged 71, also in WA. No other clues on her origin either (born c1860).
They had 3 (known) children:
Margaret Devlin HUNTER born 1893 Qld, died 1977 WA
Joseph Lawrence HUNTER born 1897 WA, died 1897 WA
John Croesus HUNTER born 1898 WA, died 1961 NZ
I have info on Margaret and John (Jack), and dates/burials/death notices for their parents, it is only the
marriage and/or birthplace of Joseph & Mary I am seeking so I can go back further. I appreciate I may need to fork out the exhorbitant Qld BDM prices for Margaret's birth cert to find out more!
Any help gratefully received.