The BDM online indexes for Victoria, Australia -
Department of Justice, Victoria, Australia - BDM Online [ http://www.bdm.vic.gov.au/home/family+history/
- list a marriage between Henry Clark and Eliza Cooknell in 1858 (as shown above in Tess’ comment).
Those same records show that Henry and Eliza had five children born in Victoria as follows:
Samuel, born in Kyneton: 1860/21119
Charles, born in Melbourne: 1862/16195
William Willoughby, born in Melbourne: 1866/22929
Thomas, born in St. Kilda: 1871/12534
Robert Cooknell, born in Collingwood: 1874/1563
To obtain details of parents of Henry and Eliza, you probably need to obtain a copy of their marriage certificate, which can be purchased online from the same site (although fairly costly).