There's definitely a lot of indecision on his part. He's at least acutely aware his grandmother is poisoning people, yet he does nothing to really stop her. It's like he just puts his hands up, and says it's out of his control. Still I can understand a lot of his actions. It's a really difficult thing to call out a loved one on something illegal, especially one you grew up with your whole life. He really did have at least enough evidence though to at least justify avoiding his grandmother, and preventing his children from ever meeting her.
True. I really didn't have a close relationship with any of my grandparents and still don't with the surviving one I have left. I mean, I care for her, sure, but I have never had that "bonding" relationship with most of my family members where you even really know who each other is at all. My family is full of very odd people. Basically, I'm saying that I can't really relate to his motivations or his reticence because I just don't have that close of a relationship with my family members. As for the family members I am close with, well, I don't suspect any of them of poisoning me...