Have you brought this concern up to him? I realize this is not an easy conversation to have, but given what you claim about your relationship ("we're practically like brothers"), you should be able to discuss it, weather the storm, and come out stronger in the end. If you can't, then your relationship with him isn't what you thought it was.
Explain to him how you feel. Don't accuse him; you're not trying to hurt him or screw him over. You're trying to work out what is right and fair.
Also, figure out for yourself what you think is right and fair. What struck me is this:
"I’ve tried working alone before and it is terribly boring and unproductive. So even though he doesn't do much for business I still like to have another person, let alone my best friend, hang out with me all day."
Based on that, you may realize that him getting 50% (at least in the past) has been perfectly justified; if it weren't for him, what would you have done?
However, the past doesn't have to dictate the future. Maybe you're at a point where having a co-founder who can actually do 50% of the "work" (beyond moral support that your current friend is doing) is important to you or to your business. Be honest about this with him, explain your struggles, desires, and motivations, and I'm confident you'll both be in a better place at the end.