Sorry, I meant to include on previous posting that the only other son of Louisa and William to have children was Isaac born 1854. Certainly, this strain of the Blackmores are the only ones to have the Parker Blackmore name so in some way you are connected - it is finding the correct strand.
I can tell you a bit about Isaac as well if you are interested. The other brothers Arthur and Harry lived together and never married - Harry was deaf. Edward never married and Robert (who was not thought to be William`s son anyway and did not carry the Parker name) married Beattie but had no children leaving Albert, my great grandfather.
Would love to hear from you so that i can fit you into my puzzle!