right now i have two litters that are two weeks apart and the moms "share" them. one minute one has them all and the next minute they are split up. it is kind of funny to see a mom with 5 babies a few days old and 5 that are a few weeks old. rats are really good moms. sharing the litters is nothing to worry about and actually is a good thing in case one mom is over whelmed the other will pick up the slack.