Height

Hi, I've been with my boyfriend for almost two years now and things are amazing most of the time. Really the only "problem" is the very slight height difference between us. I am 5'7" and he's around 5'9". I don't really see it as an issue, I like not having to stand on my tiptoes to be able to kiss him and not have him bend over to kiss me, but he's so insecure about it! Most of the time when we're standing and kissing he'll make a comment about how he wishes that he could be a few inches taller. I try to tell him that I really like his height - I love being so similar to his - but he doesn't listen when I tell him that. I just want to be able to tell him something that could help his self esteem about it, but I don't know what to say. Any suggestions??