Just to add to the mix:
Margaret Aitken, sister of George and Thomas, who married William Murray, was born in Broughton in 1827 acccording to her daughter's QLD birth certficate. Eliza Lester Murray was born on 10 July 1860 at Coochin Coochin station, to William Murray (36), b. Dalkeith, and Margaret Aitken (33) b. Broughton.
My gt grandmother was Jane Munsden Buckpitt Covington, named after her late aunt Jane Munsden Buckpitt, nee Aitken. Her mother was Isabella Borthwick Aitken, daughter of Thomas. Munsden is clearly a mispronunciation of Lumsden that has persisted, and Borthwick may well be the same. Another sister of Isabella and Jane was Margaret Murray Aitken (named after her aunt, wife of William Murray). Murray was sometimes spelled Murry and Moray.
In all, the family of Thomas Aitken (and Margaret Storey) was:
Elizabeth (1853-1941)
Isabella Borthwick (1854-1935)
Jame Lumsden (1855-1876)
John (1858-1941)
Margaret Murray (1869-1960)