Then, of course, the one you're with becomes one of those you love, especially if you're not looking while it happens. But are they ever the actual one you fell for to start with? No, never. Can you love them as much? Maybe. It depends. Do you love them the same way? Never. They're different people.
But what happens to the one you love while you're busy loving the one you're with? Can you still devote the time it takes to try and get there to be with them? Can you maintain what relationship you do have with them? Would they resent the fact that you've started to love the one you're with?
Tricky stuff, this love business.