the cert (Folio#155) shows, for the Registration district of Westminster, 1853, Parish of St Martin in the Field, County of Middlesex. Groom: William Austin, full age, bachelor, Porter, resident of Snow Hill, Father's name and profession blank. Bride: Emma Clinton, full age, spinster, no profession, residence at time of marriage Snow Hill. Father William Clinton, 'Carrier or Currier'. Married in the Parish church according to the Rites and Ceremonies of the Established Church after Banns by Minister: S Flood Jones, Curate. Witnessed by H Clinton (assumed to be Emma's brother Henry), S Crossman (either a friend, or possibly Emma's elder sister Sarah?). (There is no mention of this marriage on Emma's death cert.) 
31 Dec 1855
The Manse, Emerald Hill, Melbourne, Victoria, Australia
cert. #3632 shows: John Gibson, 30, single, born Lanark, Scotland, Master Mariner, present and usual address: Brigantine 'Express', Melbourne, s/o Adam Gibson, contractor, Janet Purdie; Bride
Emma Parker Clinton, 28, single, born London, d/o William Clinton, currier, Jemima Parker, present and usu. address Melbourne. No children by former marriage, either living or dead for either party (ie Emma ignores her previous marriage and existing child, Caroline Emma Austin).
I John Gibson, do hereby declare that I am a member of the Presbyterian church, and that I was married in the Manse at Emerald Hill. Signed by both parties. Witnesses: Andrew Boyd, Elisabeth Boyd. Minister: D Macdonald. 
It may be possible to confirm family relationships with Emma by comparing test results with other carriers of her mitochondrial DNA.
Mitochondrial DNA test-takers in the direct maternal line: