I don't know where the love started, but it goes deeper and deeper.
Some people, once they meet, will see each other for eternity; he loved her and fell in love at first sight. They were once far away from the battlefield and hatred, but in the end they just missed it. What they don't want to forget is the original them.
Some heartbeats, once they start, are irresistible; she loved him and never regretted it, just because of that second heartbeat, that bit of love, and that drop of tear.
But some fates, once intertwined, are doomed. He would rather never have loved, no matter who he gave it to, because there would have been no hatred.