Yeah, I don't get it either....
Subs, why don't you tell us about the correlation you see...because I'm really at a loss as well.
The only thing that I could possibly see is that Bert puts up with Ernie as an obligation to his brother when he'd probably rather not be associated with Ernie, or would at least rather be doing something "awesome" (like collecting paper clips or argyle socks). However, once Bert gives in to Ernie's whims Bert discovers that it's not so bad afterall.