James Cock Trethowan was the 2nd of 9 children of James and Jane Trethowan of Constantine, Cornwall who were married 11 June 1833.
This bloke had a brother named Henry Iconium Trethowan baptised in Constantine 2 June 1839.
He was with his parents, brother James Cock and several other siblings in the 1851 census.
It is possible that Henry came to Australia at about the same time - Dec. 1858 - when James Cock arrived, however there is only a transcription of the passenger list on FMP and there is no record of Henry's arrival, however events following proved that he did arrive sometime:
1] He married Susan Ann Richards in 1867 - registration #1445 - possibly in Creswick, Victoria.
2] He and Susan Ann had 5 children:
Albert Henry - 1868 - Creswick - #2050
Alfred James - 1869 - Crewsick - #21740
Lambert William - 1871 - Bung - #21807
Henrietta Emily - 1872 - Bung - #21822
Frederick Herbert - 1875 - Bung - #899
3] Susan Ann died 1875 - possibly in Bung - registration #825.
With 5 young children Henry immediately married [1875] Agnes Wilhmeiner[sic] Anderson - #3694. I have not found the births of any children nor have I found a death for Agnes, however in 1887 he married Bessie Sutcliffe - #2363.
I have absolutely no info whatsoever on these 2 ladies.
Henry Iconium can be found in 1909 Electoral Rolls in Echuca, Victoria and I believe he died in 1910 age 72 - source - Australia, Death Index 1787-1985.
Any help on him would be appreciated