People are not meant to be owned. And love is not meant to be forced.
If you truly love someone, then you should be happy with whatever makes that person happy. You can't force someone to love you back if they don't. If someone doesn't like/love you the way you want them to, all you can do is let them go. Some people are not meant to stay in our lives. No matter how long or short they have stayed in our lives, they are just passersby who share a part of their lives to us.
A passage from Paulo Coelho's The Alchemist says: "We are travelers on a cosmic journey, stardust swirling and dancing in the eddies and whirlpools of infinity. Life is eternal. We have stopped for a moment to encounter each other, to meet, to love, to share. This is a precious moment. A little parenthesis in eternity."
This is of course under the assumption that you have told the person that you love them and you want to pursue them. If not, tell the person about your feelings first and if the answer is still no, respect their decision.