I am 20F and I need to know whether it is a mistake or sin to like someone (20M) who is already in a long distance relationship??

I am 20F.I really like my cousin 20M and recently confessed my feelings to him to which his response was vague.He said that he is already in a 2 yr ongoing relationship (though I wasn't aware of such a relationship).Neither he said a Yes or a No but he did say that he too liked me in the past but didn't confess because he thought he wasn't my type. Since I didn't want to be a third person in their relationship, I said that I will not be disturbing him anymore to which he replied me that we can be friends. I agreed to such suggestion disheartedly (as I cannot consider him as only a friend and that he is so good).Idk whether he too considers me just as a friend or is there anything more than that.I cannot understand him as he is not really good at expressing his feelings.He texts me often.We are in touch.At the end of the day, I still like him.What am I supposed to do as I do not have the heart to block him and that I cannot see him as a friend.