My five year old son has this daily behavior where he screams out random sounds over and over until we tell him to stop. Sometimes he will do it again, once or twice even after we are looking at him and asking him to stop, and then immediately says sorry, but he yells it...I'M SORRY, I'M SORRY, over and over until I hold his hand and say use a quite voice. He also clicks his tongue or his mouth, or snaps or bangs on stuff excessively and repeatedly while watching tv, drawing, or gaming often switching between any of the above mentioned things. He has twin autistic step brothers that are 8 and at first we thought he was doing it to get attention and because the boys don't like it, he gets negative attention from them when they yell "BE QUIET!!!!) while I do believe sometimes it is done on purpose to instigate, most of the time, they are at school and he is alone and doing it. He shows no other signs of any other behavior problems. He is extremely smart. He is already reading, computing math problems, some of them two digits, all in his head. He never stops talking, except when he's clicking. He's always asking questions about everything, and when we give him and answer he has to think about he starts pacing and clicking.
Should I be worried about this? He has two older biological siblings that do not show any of these symptoms, so I am at a loss.
Thanks