Words we've always known.

Since the day you are born, you have tattooed somewhere on your skin a sentence, those words will be the ones that make you fall in love with your soulmate, Liam is stressed by the fact that instead of a sentence, he's only got a single word. Theo has two.

Or, alternatively, the one in which everything is exactly the same except Liam and Theo are aware of the fact that they're soulmates.