SIBELLA 1848
DAVEY, Henry (from Worchester), wife,
DAVEY, 3 children and another born on voyage on July 1st
http://trove.nla.gov.au/ndp/del/article/48727628 South Australian Register 19 July 1848
Henry Davey wife three children (one of them a daughter, born at sea on 8th July)
http://trove.nla.gov.au/ndp/del/article/158926343 Adelaide Observer, 22 July 1848
Henry Davey wife and three children (one of them, a daughter, born at sea on 8th July)
I am not sure about fares to South Australia, but to me, 'children' indicates that the fare paid was for a child .... I wonder at what age would a lad or lass need to be, to be noted as 'single male' or 'single female' rather than a child, part of a family if travelling in 1848 from the ports of London or Plymouth.....
The newspaper cuttings do not give the gender of the two older children....
Did our OP's family actually arrive on that voyage
Cheers, JM