I have 2 peach faced lovebird and i want to know if I could separate them?

My friend left for the summer for 6 months and gave me a lovebird to take care of until he came back. I ended up buying another one. The birds know each other from flying together and from being in separate cages. Could i give his one back and keep the other one and just have them meet whenever I can get to his house? Would that not be good for them??