They' re grown ups now and should have been able to make up their own minds, surely they have memories that can decipher the sh1te from the reality, if they have not been able to do this then they really are brainwashed, but in this so called enlightened age, when so many people have been revealed to have suffered this sort of torment, they surely cannot have carried on into adulthood believing their Mother's fantastical lies. There should now be a social worker involved in negotiations to reestablish a family bond that the woman destroyed, i would contact social services, because in the long term, your brother may well find himself in need of support from family and the social services are going to be aware of the burden it would lace on their resources if he did not have living relatives to be with him.