This is the one in the same David Morgan Llewellyn that I found on the 1881 census. He is listed on the 1901 census as Daniel Lllewellyn.
It is a bit of a puzzle as I have seen a copy of his death certificate and he died in May 1961 aged 88 years, which means that his date of birth should be 1872.
I think I will have to bite the bullet and speak to my relatives again and see if they can shed anymore light on it.