John MacKenzie/John McKenzie and Margareth Brown: England to Australia - help!!

John MacKenzie (aka John McKenzie) was born in 1820 in Plockton, Ross shire, Scotland. He was the son of Donald McKenzie and Margaret (Surname Unknown). He married Margareth Brown (dau. of Samuel Brown and Catherine Philpott) in 1849 in London. In London, Margaret (1851) and Alexander (1853) were born. The family then immigrated to Victoria (Australia) but the date is unknown as to when this occurred. In Australia (in the Mt. Egerton/Mt. Blackwood area), John (1855, m. Liebenner Venville), Angus Findlay (1857), Samuel Thomas (1859, m. Mary Jane Gidlow), Isabella Catherine (1862), Mary Rebecca (1865, m. Alexander Venville & Joshua Widdison), Donald William (1866, m. Jane Downing), William (1868), William Frederick (1870, m. Adeline Clara Lyons), and Edward (1872) were born. Does this tie into anyone's research? I'd ideally like to try to trace the family back further but I'd also love to find out more about these individuals. Please contact me if you can help!