Percy pulled Annabeth close and kissed her…long enough for it to get really awkward for Piper, though she said nothing. She thought about the old rule of Aphrodite’s cabin: that to be recognized as a daughter of the love goddess, you had to break someone’s heart. Piper had long ago decided to change that rule. Percy and Annabeth were a perfect example of why. You should have to make someone`s heart whole; that was a much better test.
Rick Riordan, The Blood of Olympus