Cornelius was Louisa Sheaf's brother - he and another brother Aaron, and their father Aaron, were all in trouble with the law at different times. Life was probably pretty hard for them all after the loss of Elizabeth and Constance.
sparkgirl - I have an Elizabeth Silvester as James Clark's wife, married 28 May 1797 St Mary's, Portsea, Hampshire, England, however I got this from other people's family trees, and I am not entirely convinced this is correct. This Elizabeth was born in Farlington, Hampshire, which doesn't fit with the 1841 census record, and neither does her age, as she was born in 1773 so would have been about 68 in 1841, not 60.
Other family trees also have two older siblings James (born 1795 - illegitimate) and Harriet (born 1798), but then there is a huge gap to Leah born in 1812, so I am wondering if James Clark and Elizabeth Silvester, with James and Harriet, may be a different family?? Have you come across them?
I also have another sibling for Leah, Jacob and Esau, and Adam - a sister Emily, born in 1817, but I can find no other records for her.
Had another look at the 1841 census record, and there is a mark in the final column, where it indicates if they were born in Scotland, Ireland or elsewhere - it could be an I for Ireland ??