Clayfinch on Family Tree Circles

I am looking for descendants of the artist David Cox jnr. The only knowledge I have came from my great aunt Maud Cox. She and her sister were adopted by Harry and Minnie Cox. As a young child I visited regularly at their home in Sandhurst Road, Moseley, Birmingham. I recall sitting with my uncle Harry and I once met Cuthbert Cox. My grandmother Elsie May Cashmore married Ernest Arthur Cox and they had two children my mother, Alice Marguerite Cox and Beryl Lilian Cox both now deceased. My great aunt told me many stories about David Cox the artist. However I cannot find a link but I know somewhere along the line I am relatied to him. I was told that he was my great great grandfather. Can anybody help me?