How do Rhett and Link work together?

Already, the fact that they managed to stay together their entire lives in absolutely amazing. But really, in my opinion, they have a little bit of different dynamics. Link is smaller, i find that many people find him, "cute and adorable..." Perhaps because he's always smiling and dancing? And don't get me wrong, rhett can be happy, he just nessicarly doesn't seem like it, if you ask me, he seems a bit grouchy, or hurt even? I don't know, i rarely see a soft gentle smile from him, yes he's got a lot of laughs, but link is different, it's more childish for him, he even talks about how he doesn't like to consider himself a full adult. So, how can they be so different, yet so alike, and stay together for a lifetime?