Obviously, Nameless is Jacob's brother, Esau.
Re-reading the story of Jacob in Genesis there's many similarities to the storyline on LOST. My guess is that Nameless was once the owner of the island and he sold it to Jacob cheap and accused Jacob of stealing it from him. I am pretty certain that Nameless is also the smoke monster, or can pretend to be the smoke monster.
On a side note, The guy that played Jacob was in the CSI season finale with The woman that played Libby on LOST.