Answer: Unless your brother is willing to negotiate, you have few alternatives besides litigation. As co-owners, you both have the right to possession of the entire house. Co-ownership can often make the co-owners reluctant roommates. Each of you also has a near-absolute right to force a sale (or split) of the property through a specialized kind of lawsuit called "partition."
Partition lawsuits are very difficult without the assistance of an attorney. If your brother decides to fight the lawsuit and take matter to trial, it can become expensive and take a long time. When faced with a partition lawsuit, the once-unwilling owner often becomes much more willing to negotiate an out-of-court solution.
Sometimes the solution is a buy-out; other times, the parties agree on a sale, in which case, if there is an on-going dispute over how much money each is entitled to (the net proceeds in a partition sale are divided the same as the ownership percentages AFTER adjustments for excess outlays made by one co-owner for mortgage payments, property taxes, insurance, necessary repairs, etc. and for rents received by the owner in possession from third-party tenants), the owners may wish to agree to have that handled by post-sale arbitration.
If all else fails, you can hire a lawyer to prepare and file the lawsuit, but you should instruct the lawyer to keep pressing for a negotiated settlement.
About the Author: Carl H. Starrett II has been a licensed attorney since 1993 and is a member in good standing with the California State Bar and the San Diego County Bar Association. Mr. Starrett practices in the areas of bankruptcy, business litigation, construction, corporate planning and debt collection.