Depending on their history, twins may also be at slightly different developmental stages: many twins are born slightly prematurely, but some also emerge with significantly different birth weights (as can happen with twin-to-twin transfusion syndrome). You may well find that you have a nine-month-old and a sevenmonth-old (corrected age) at home, even though your twins were born on the same day! One baby has developed object permanence, while the other still thinks a toy that’s been moved out of sight ceases to exist! And for that reason, your babies’ discipline needs can differ, too. If one twin is hitting the other with a block, you may remove the toy from the “nine-monthold” to howls of protest, while the “seven-monthold” may barely register its loss. Saying “no hitting” and demonstrating sympathy and concern for the injured twin is a better strategy here.