Reading alot of theories about Jacob and the relationship between him and them man in black. Personally i can't grasp the whole Jacob is good otherman is bad scenario. Neither one looks to be good nor bad they both hold strong views of peace yet violence as well I.E Otherman"You know hoe badly i want to kill you" yet he see's the human race outside the island as a corruptive destroying society that always ends the same . At the same time we wonder what their motives with the island are. We can assume that their higher beings or so forth or maybe something much more spiritual.
But as for those 2 relationship im just gunna say this with no evidence but, i think that those 2 are father and son.. The father can;t kill his son, but disagrees with his "motives". Thats all i got we'll just have to wait and see