Clearly, from the way you describe things, the partnership is over. It's time to find a way out, and perhaps that's really what you're getting at: how to properly end the business (at least in its current form) to allow you to get your fair share out of it (and I'm assuming, you're OK with everyone else getting their fair share out of it as well).
This really depends on the local laws where you live. Typically, though, the first thing you'd look at is any contract you have in place. This might include Articles of Incorporation, Articles of Organization, or other founding documents. Hopefully, you went through the process correctly, and you've got what you need to figure it out. Short of any formal contracts, most countries fall back on written communication, and if there's none of that, then maybe verbal communication. But of course, as you get down to those levels, it starts to become a he-said-she-said kind of thing, and it tends to fall apart.
If I were in your situation, I'd call them up and say, "Hey, we've got to talk. Clearly things are falling apart, and it's time to formalize how we end this business venture." If you can't all agree to something, it's very likely to end in arbitration or court. (Might I suggest, do your best to be as friendly as you can; if you come in on the attack, they'll fight back, and it will only make things worse.)
Look at the contracts you have, talk to them, and talk to a lawyer.
Then move on and start again.
Businesses come and go all the time; you can always start over. If you've designed a logo and paperwork before, it can be done again.