Hi all, quick update:
I contacted grandmother who says that Charles Greenwood first came to Adelaide from England, possibly North West England, apparently already married. First wife died aboard the ship, so Charles then remarried, possibly on ship.
After arriving in Adelaide, that second wife also died, and Charles subsequently married her sister in Adelaide, who then also died. At that point, the family apparently kicked him out, after which I presume he moved to Melbourne and married wife no. 4? Johanna O'Brien. After "Annie" O'Brien died in 1890, he apparently moved to Tasmania, but not much more is known of him after that. I still don't know who exactly raised son Herbert, but there was apparently a sister "Dory", but more children were probably born to other wives also.
The only Charles Greenwood arrival in Adelaide that I could find was aboard the "Earl Dalhousie" in 1875, aged 22, single, carpenter, UK Assisted Passenger I think.
http://www.theshipslist.com/ships/australia/earldalhousie1875.shtmlIf this is the same Charles Greenwood, then he was likely born c 1853.
Haven't yet found any info from his time in Tasmania, but he probably died there.
Unfortunately I still don't have wives' or parents' names yet, but it seems this story is much more bizarre than first assumed.
Thanks for all the replies so far!