I've begun taking Nathan to a psychologist to deal with his anxiety. I'm hoping that giving Nathan someone objective to talk to will help him to unload some of these dark thoughts before they can brood in his mind.
Of all the family members, I think Nathan has the hardest time. Dave and I are adults and although Alex's behaviour is hard on us, we have the emotional and physical resources to cope with it. Nathan has to deal with a great many restrictions due to Alex's capabilities and he is often the brunt of Alex's misbehaviour and aggression. He doesn't get be the decision maker, so perhaps its not surprising that he seeks to exert control wherever he can.
Nathan is also sensitive, worrying about Alex and the family, no matter how much we tell him that the adults will take care of it.
It's a tough situation and he needs support of his own to get through it.