Vincent was tempted to go over to Graham's house to strangle the man but the thought of seeing his uncle be killed by the same creatures he killed his brother with was holding him back.
Vincent never had that emotion of wanting something from Victor so badly that he would feel the need to kill his flesh and blood. How greedy do you have to be to kill your own brother and then feel no remorse to try poisoning your nephew after?
He was a little annoyed that his father had not dealt with Graham instead of seeing the goodness that did not exist. If Victor were to ever be a threat to Aurora or their children, as much as he loved his brother he would choose to protect Aurora and the children.
His father didn't have to kill Graham. Locking him away somewhere would have been enough or simply not fighting beside the man who could point his sword at you.