Finn (Cory Monteith) recently broke up with Rachel (Lea Michele) after she was unfaithful to him. However, he is now dating Quinn (Dianna Agron), who previously cheated on him.
Speaking to Zap2It, Murphy suggested that the storyline "causes conflict" and added that it does have a realistic element.
"Quinn is Finn's first love," he said. "Think about the first person you were in love with. That's a fascinating relationship, that first real love. I would forgive my first love anything, but not my second boyfriend. Plus, [Quinn's] the temptress."
Meanwhile, Falchuk suggested that Finn may be able to forgive Rachel in the future.
"People are complicated," he said. "Just because he doesn't forgive her now doesn't mean he's never going to forgive her. He forgave Quinn eventually, he'll forgive Rachel eventually."
Glee returns for a new episode in the US in April and continues in the UK on Mondays at 9pm on E4.
> Cory Monteith: 'Finn, Rachel are endgame'