A question

So this guy I like, he’s in a relationship, and I respect that, I wouldn’t cross any boundaries. I’m a firm believer in what is meant to be mine will come to me, but at the same time I am wondering if he should know how I feel about him, because I’m pretty sure he had feelings for me in the past, and I didn’t realize it at the time, so I just dismissed it as him being friendly. So a part of me wonders if he would go for it if he knew how I felt. Should I tell him how I feel, or let go?