female gerbil torn between two brothers

Question
First, I had a male gerbil and a female gerbil and they had a litter of eight babies together. By the time the babies were weaned, my cat had attacked my gerbils. She killed the mom, the dad, and most of the babies. Only two brothers survived and I made sure the cat wouldn't be able to go near them again. Now I have another issue. The brothers eventually became adults then I introduced a young gerbil to them. The brother gerbils were very welcoming and nice to it. Before I bought it, the guy from the pet store told me it was a boy, but I found out the hard way that it's a girl because about two months after bringing her home, I noticed that she's pregnant. She got fatter and I gently rubbed her belly and felt things moving around inside of it. My concern is that the brother gerbil that did NOT get her pregnant will try and harm/kill the babies. I don't know which one of them impregnated her because I didn't see any of them mating with her. So what should I do? By the way, I know for a fact that she wasn't pregnant when I brought her home because a gerbil's pregnancy is only like 20-something days long and I had her for over 2 months already.

Answer
Hello Rob,
if you aren't sure which one is the father, you could take both males out of the cage and put them in a seperate cage. That's also good to ensure she doesn't get pregnant immediently after giving birth.The mom can raise the pups by herself and she will do just fine that way. It would be hard to figure out which one was the father with two males being in the cage.