Are rats happy in a pair?

I’ve recently lost one of my 19m old boys from my trio. Will my two remaining boys be happy enough by themselves or do I need to get more? They’re both happy and healthy and I suspect they’ve got a lot more time. I’m not ready yet to get more but I’m worried that they may get bored/lonely if I don’t so I’m definitely open to it in the next few months. What would people recommend?