This is an extremely difficult question to answer. There many possibilities none of which you or I could know the answer to for sure. Many people who do abuse others were themselves once abused. It is possible, and highly likely, that your brother was abused by someone else or a family member and this is why he abused you. Having been abused does not necessarily mean that one will go on to abuse others, but it does increase the risk that the abused will begin to abuse others. I cannot say if your brother has a disorder per say but because I am not familiar with his background and history. I do know that there are no specific mental health disorders in which the capacity to abuse is a symptom. Additionally, I do not think that your brother’s abuse towards you was an experiment gone wrong. He simply is an abuser and the reasons he became an abuser are difficult to know.
With regard to your concern about his children, I do think your concerns may be warranted. You are a survivor of his horrific actions. You experienced first hand what your brother was capable of. Breaking your silence is a tricky issue since you have no way of knowing if your brother would abuse his own children. I do think that he may be more likely to inflict abuse upon his children since he does have a long history of this type of behavior. Alternatively, he may have gotten treatment to deal with the issue or would never harm his children in this manner. I do not think that breaking your silence at this time is the correct action unless you suspect his children may be being abused. As I mentioned earlier, your brother may have gotten treatment or would never abuse his children. If the two latter possibilities are true in this situation and you bring the past abuse by your brother to his wife’s attention, you could start a horrible family battle, one in which may end in divorce or the separation of his family. The best advice that I can give is for you to pay attention to the behavior of his children and his relationship with them. If you see your brother behaving in a way that you recognize to be related to abuse then consider breaking your silence. I am sorry that I could not provide you with a more concise, black and white answer but there are no easy answers in this situation. It is an extremely complex situation. Please write again if you have any more questions.