I think we have discovered the same people. I have had a lot of information from the website you mentioned too - very useful. I think that the Ann Allen marriage may be another generation earlier so I have a note of it.
I think Robert Jarvis Kemp b 1812 was son of Joseph Kemp and Mary Jarvis. He had siblings Malin 1809, Sarah 1811, Joseph 1814, William 1818, Henry 1819 and Edwin 1821. I think that Joseph senior's parents were the John Kemp and Mary Kelk I mentioned before. It was Joseph's brother, John, who was the Sheffield cutler but I think that he changed occupation and, by 1829, was back in Tickhill as a grocer/draper.
I cannot spot a link between this family and that of Charles Kemp who married Mary Matthews. These seem to be the butchers. Do you have one?