Jill, I can't find the proposed parents in the census. Where are they?

Re your ancestor William Kewley age about 5 missing from 1851, I thought I was onto something with William KALEY, Nephew age 6 Scholar b Liverpool at The Quay, Frodsham, Cheshire . The head of family is Samuel PENKEMAN 68 Sawyer b Cheshire Frodsham and his wife is Catherine 58 b Isle of Man Laxey. I found their marriage on the 1GI 1 Mar 1835 Frodsham, Samuel PENKEYMAN to Catherine COULEY. I think this will turn out to be COWLEY rather than KEWLEY.

Obtaining the certificate will be useful. Your ancestor William is also there, though there is more than one possibility in the index.