To-day whilst searching through an immigration index I came across an entry for Samuel and Amelia GILL; nothing too out of the ordinary about that, you say.
The ship they arrived on was the Western Monarch which arrived in Brisbane on the 27th of March in 1876.
Now Samuel was the younger of the two at 65 years of age and his wife, Amelia, was only 72 years old.
Now I haven't done any research on these two people but there is a Samuel GILL who has died on the 3rd of October in 1886 and his parents were George GILL and Elizabeth (unknown). And there is an Amelia GILL who died on the 27th of July in 1891 and her parents were George HUTCHINSON and Mary WOOD. Both Samuel and Amelia died somewhere in country Queensland.
There is no other mention of Samuel and Amelia together in Qld bdm index, ie. not asoicated with any other birth or death.
Looking in Trove there is a death notice in 'The Queenslander' on the 8th of August in 1891 which reads, "GILL, On the 27th July, at the residence of her son-in-law, Thomas Pownall, Cambridge Street, South Brisbane, Amelia Gill, relict of the late Samuel Gill, in her 90th year."
The same notice also appeared in The Brisbane Courier on the 5th of August 1891.
They obviously came to Australia to see or be with their son Thomas, but that is surely some trip to make at their age.