They have to work it out before they close. Ideally they would work it out before they put the house on the market. Or, if they already have an offer, before they sign off on the offer. In reality most partners have an agreement for ownership percentages when they purchased the property.

Did your brother and his friend have a prior agreement or did they just let that part slide?

There isn't a law that requires partners to split proceeds evenly or in any particular manor. In an extreme example one partner could have 1% ownership and the other 99%.

How have they been dividing up the expenses during their ownership period?

This should have been put in writing at the time of them buying the house in the first place. If I was having problems like this, I doubt they would improve. A consultation with a real estate attorney or an arbitration service is in order right now.

Their deed (how they took title) will dictate how the proceeds from the sale are split up. They are probably joint tenants. The percentage of ownership should have been agreed upon in writing at some point.

There are so many things that were happened during the ownership. Do you have all those things specified on a legal document?

Before putting the house into the market it is mandatory to know all the legal rights. I would request you to contact a real estate attorney.

Thanks

Lazaro Perez