Your family story has been a bit garbled, because your great grandfather doesn't seem to have been named after an actor, but rather after a character in a play. Perhaps your great-great-grandmother was fond of an actor who played the character.
Claude Melnotte is the hero of a play called
The Lady of Lyons by the English author
Edward Bulwer-Lytton. You can find information about the play here:
http://www.encyclopedia.com/doc/1O149-LadyofLyonsThe.html
Melnotte does seem to be a real, if rare, French surname.