Can you put two female and two male gerbils together?

no. when the pups are born the non pregnant gerbil will kill the pups and most likely attemp or actually kill the mother too. but if the mother dies in birth the other gerbil may adopt the pups. take it from someone who knows.

I disagree, if two females are raised together for a long period of time, they can be kept together if one has pups. I have raised gerbils a long time and usually the 2 females will raise the pups together.