Steve, there's nothing wrong in backing out of a relationship with inheritance in mind, but it didn't mean that he wanted to help himself before either parent's time was up. JB was beginning to come to his senses and following his head instead of his heart----well his father's head as JB's was half-empty.
Perhaps you'd care to explain, what, of Jeremy's behaviours, has led you to the conclusion that "JB was beginning to come to his senses"? It was actually "following his head instead of his heart" that caused the problems. Young men don't screw around with their hearts, they do it with their heads. It probably also follows that if he was thinking with Nevill's head it was the wrong direction for him.