Personally for me, the word 'love' is a big word. Some dictionaries even define it as an "intense feeling of deep affection" or a "deep romantic interest", keyword here being deep and intense.
So if you are really asking about love "love" (real or true love) then NO, I personally believe that one cannot completely unlove someone whom he/she shares an intense or deep affection before especially if that love was also reciprocated.
Even if their relationship didn't work out, I believe that a part of them would still make them subconsciously care for each other provided again that the feeling they are experiencing is real love. If what they are feeling is just "like", "admiration" or a simple "attraction" then one can completely get out of that feeling through the passage of time. XD
It's normal to stop caring for someone whom you only thought you loved.
If you truly love someone then you cannot unlove this person ever.
This is my opinion at least.
Well, if you really loved someone, you can't not love, but all you can do is let it go.
You can stop letting their story or memory make sense to you today.
You can try not to hate them as you greet the future you imagined them with, give up all the dreams you shared with them, say goodbye to everything you wanted to share with them or all the places you wanted to visit with them. .
You can let them fall in love again and realize that there is nothing to be sad about.
You can never really forget or love someone, but you can surely free him.