I think it's about knowing somebody so well that you understand everything about them, almost to the point that you will think things the same way, you are almost the same, in a sense. And even when you aren't together, you can feel what they feel themselves. A deep kind of empathy. It should be, "I am me, the universe, and you", as in, "We are the same person, same entity, same soul" - Soul mates, maybe..?
I think it's about knowing somebody so well that you understand everything about them, almost to the point that you will think things the same way, you are almost the same, in a sense. And even when you aren't together, you can feel what they feel themselves. A deep kind of empathy. It should be, "I am me, the universe, and you", as in, "We are the same person, same entity, same soul" - Soul mates, maybe..?