A: Well let's start with an underlying assumption you are making. You say you don't want to hurt neither of them, so the question I have for you is how do you know you will? Have you specifically defined where your relationship is with your boyfriend, not only to yourself, but also shared this with him. What if you have outgrown each other and you are basing these assumptions off of irrelevant information. And I am not saying that you are, just something for you to consider.
Because the truth of the matter is, I am not going to tell you what to do either way. This is a decision you will have to make for yourself. And it would be foolish of me to give you any advice based on such little information.
So what I will suggest is for you to consider looking at some things such as, you say his cousin fell in love with you. What are your feelings about him? Remember to look out for yourself as well. Where are you in this web?
Something else to look at is your own personal criteria for a boyfriend. How well have you defined what it is that is important to you in a mate and in a relationship?
These are just some starting points. Ask yourself some more key questions to get a "real" answer from yourself.
-Oz