I think what the boys really need are time. I have to say that when encouraging the kids towards their walk away parent you must do very carefully! If you talk too much, they get annoyed and don't even want to discuss it. If you keep it short and sweet, its a seed planted and it grows with the proper nurturing.
It sounds to me as if GM is choosing to be neutral. This is ok. I agree to hold on to whatever paper trail or evidence of behaviors her husband may have incase this were to get really nasty. But to blow smoke on to her very own son's just for co parenting sake for her H is not a good idea.
I've been down this road with my girls. They needed their space to process it all and come to terms with their feelings and how to handle them. It took 3 months for them to come around after they were at the point GM's boys are at.
I talked with them, I listened to their feelings and we discussed how they felt. I told them it was their choice, and also encouraged them to speak to their father about things. I've found its best not to get involved or in the middle unless it's seriously warranted.
