XXXXX XXXXX, XXXXX XXXXX XXXXX, and George XXXXX XXXXX appear to be the same person. As for James, he is probably a brother but you did not request research into George's siblings. I do not believe your George is the George that arrived on a ship on 18 Dec 1865.
Following is a list of the records I have located;
Australia Birth Index, 1788-1922 - for XXXXX XXXXX
Australia Death Index. 1781-1985 - for U. Thompson
Australia, Electoral Rolls, 1903-1980 - for Henry XXXXX XXXXX
Tasmania, Australia, Index to Death Notices in The Mercury, 1854-1930 - for Thompson
Australia Death Index, 1787-1985 - for Henry XXXXX XXXXX
Australia Marriage Index, 1788-1950 - for Henry XXXXX XXXXX
Record of Death - for Eliza Thompson
Henry XXXXX XXXXX, son of U. and XXXXX XXXXX, was born in Hobart, Tasmania on 10 Apr 1851. On 17 Sep 1873 George married Eliza Dickinson in Longford, Tasmania. On 16 Jan 1918 Henry XXXXX XXXXX died in Richmond, Tasmania.