Well done on the new babies horsey. Hope mum is now separated from dad though!
!! Baby gerbils are just adorable. Make sure they are sexed and split at the correct ages though and paired up where possible. Females should really only be kept as a pair while male gerbils can live in smaller groups, but ideally, pairs are best. De-clanning in gerbils can happen at anytime with adults which is why it`s better to keep them in pairs in a decent sized tank. It`s good that she only had four little ones so hopefully they will be two males, two females or all the same gender!
The female babies could possibly stay with their mum but any male babies will need splitting away when they are weaned and at that stage where they could get the females pregnant, but make sure you know the day/date they were born to determine their exact ages. Put that on a calendar to remind you and after five weeks or so, they should be mature enough to tell which genders they are. x