I have 3 weeks twin boys. one twin i think there might be something wrong with his jaws because he is always opening closing it as if he is shivering. should i be worried?

Normal: Newborn babies have immature nerve reflexes which leads to overactive muscle reactions. A high number of them exhibit lip quivering, yawning, mouth opening and closing or chin twitching. Others don't exhibit any of these. This is normal. Things to call your Dr about include: blue lips, uncontrolled rhythmic twitching of arms/legs, fever above 100.4, or strained breathing.