Hi Meredith. We may have two different branches of the same tree here. The earliest William that I have listed was born 1801 in Guiseley. He married Sarah Ellen Crowther and he died in 1880 in Toronto.
The first Charles Cawthra (no "Y") I have is Charles Martin Cawthra, born 1870 in Rochester, New York.
I have no listing of a Joshua.
The earliest listing for a wife named Mary that I have is Mary Brown marrying Henry Cawthray in 1754.
I know this isn't exactly helping you but if you get any more info, maybe something recent, I'll be happy to look through my notes. Good luck!