Play-fighting gerbils will gently roll around with each other in a way that looks like wrestling. If kept in pairs or groups they will spend a long time grooming each other. To carry out this bonding session they sit on top of each other and comb through their companion's fur, searching for parasites and dirt and smoothing out tangles. They comb and lick themselves clean too.

Gerbils are very fastidious when it comes to cleaning themselves. Gerbils sometimes like to groom each other. The gerbils will hop around together side-by-side or one following the other. If a chase begins, a fight can start. They’ll sit on top of one another and comb through one another’s hair, searching for insects and smoothing out tangles. Even a single gerbil will spend some time keeping itself clean. The pushed one can kick with his hind legs or just free himself and push the other. Boxing.
Grooming reinforces the bond between gerbils in an enclosure together, and … It's a good sign when your pets do this, as the behavior means they’re getting on well. Gerbils Grooming Each Other.

This is when gerbils stand on their hind legs and playfully bat each other with their front paws.
Gerbils are very clean animals and if kept in pairs or groups will spend a long time grooming each other. The act of grooming reinforces the bonding between the pair and also the dominance within a group of gerbils. From time to time, you may notice that your gerbils are grooming each other. One of the gerbil will push the other one on his side. They do not hurt or bite one another during this. Wrestling. They can groom each other after that or they might just go back to their normal activities.