The first time it happens, it's Kurt's fault.
He shouldn't have taken Chandler's number at all.
Blaine is right. It is cheating.
Before his mind's even registered the inconceivable reality - Blaine just hit him – Blaine is on his knees in front of Kurt where he fell on the edge of his bed, the tears that have been in his eyes through this whole conversation spilling over as he begs for forgiveness in a panicked, sobbing voice.
Kurt can only give it to him. After all, he needs forgiveness, too. This just makes them even, right?
Until the next time.