Shamu sure has some kind of disorder, which I do not the name of.
At the dining table when Aarushi declared that she does not want to wait and want to marry Aman at the earliest, he started shivering. Then when Adarsh tried to reason her, Shamu expressions changed as if he is thinking 'God, why is Adarsh opening his mouth against Aarushi, now how am I going to solve their differences'. His focus totally shifted from the main point in the conversation.