Hi Jane and Deb,
Thanks for your efforts and information.
As far as I am aware, only William and his wife Eliza Lavercombe emigrated to Australia. His children were Mary, Anna (x2), Henry Arthur, William, George, Eliza and Herbert, all born in Australia (except Mary who was born on the voyage and died soon after arrival). His father John is listed as an ag laborer on William's marriage certificate.
I wonder if the family Jane found on 1841 census is his family but given that William would have been approx 15, could he have already been off working for someone else??