To answer this question, another question needs to be answered: Is it possible to love more than one person at different times? In other words, is love a once in a lifetime experience or something that can happen more than once?
I think that most people would agree that it is possible to love different people at different times. Love can happen again. It would be depressing to think that if you loved a person, then for whatever reason that person is no more in your life that you are not going to experience love ever again. But it is not only depressing but also unrealistic to believe that.
So now lets consider a hypothetical scenario where a person loved more than one person at different times:
Let's say it was a girl who met her first boyfriend in high school. They loved each other, they were fond of each other. Unfortunately life happens, and her boyfriend's family moved to another country and her boyfriend had to move with them. Few years later, she was in university, she met a gorgeous guy, and one thing lead to another they were madly in love. The years go by, and life happens once again. Couple of years later, she meets yet another lovely guy they have so much in common, and right now she is happily engaged to the guy.
It is reasonable to believe that the girl in our scenario had sincere feeling towards all three guys. And it is imaginable that those sincere feelings are all instances of love.
So now, let's imagine a different storyline about those same people, but that they were all classmates in high school. Now, from the previous storyline we know that the girl is capable of having sincere feelings of love towards all three guys. However, the dilemma lies in the fact that she met them all at the same time.
So the question now is: Could she possibly love two or all three of those guys at the same time? Does love transcend the limits of time? Or is she destined to love only one of them?