helens5162 on Family Tree Circles

Joseph James Cooper b,1813, London was married to Hannah Randall b,1811, Wiltshire, England. They travelled on the "Commodore Perry" to Sydney in 1856 with their 4 children. Jane b,1841, Mary b,1844, Harriet, b, 1846 & Joseph b, 1848. Joseph, Hannah & the children (except for Jane) show up as buried in Utah in the very late 1890's & thereabouts. Why would a family travel agin the distance to the US? They are not on any passenger lists I have looked at.
Any connections would be greatly appreciated.
Regards Helen