BABY MICE please help me thanks!?

my pet mouse just had babies! :) my question is i have one other mouse in the cage that's a boy but hes not a grown mouse yet hes still a baby his self. and i need to know can i leave him in there with her and her babies?? will he hurt them?? this is my first time havin a mouse that's gave birth so i really dont know much, i bought them not long ago not knowin she was pregnant so this is a surprise for me. i bought a mice book on the internet to learn more about them but i havent gotten it yet and also ive tried lookin up stuff online to read about this but i havent found anythin to answer my question. please help thanks! any other advise anyone has to would help alot! :)