Sorry - writing too fast - I meant to say "how do you know that the Ann Kneale (born about 1830 Kirk Michael) is the illegitimate daughter of the John Kneale you have found in the 1841 census?"
Was she with him in the 1841 household?
Was her father given as John Kneale with an Andreas address in Australian certs?
Does her birth date also come from Australian certs? No baptism?

Sue