Yep what Judy said. As long as the females get along and the other one is about to drop her own litter it should be fine. I like having my female rats one per 10 gallon tank with her litter but I've communal housed them a couple of times. Just watch that there isn't a lot of pinkie stealing going on and that the pinks have big fat milkbands visible. I'd pull dad out though as he will likely try to jump the females immediately after they give birth. If you don't want to though do know that rat males make excellent parents and the chances of him harming his own offspring are next to nil. Adults both male and female may cull pinks if they are unsound or inferior but rarely eat them for no reason as is more often seen with mice.