Thanks for your question.
I'm afraid that your brother can make an application to Court to force the sale of the property by way of a Court Order. Although you would be able to make representations as to why it should not be sold in practice these orders are seldom refused.
Unless there was an agreement to the contrary as to the extent of your interests in the property then there is a presumption that you hold 50:50 shares.
If the house is in negative equity though then you should try to reason with him by stating that the mortgage company will seek to recover the arrears from both you and him. You should try and persuade him to remain on the mortgage for the time being until the property has recovered in value and is no longer in negative equity.
This will afford you time to re-finance and, if possible, obtain a mortgage offer at a later date. State that if you cannot do this at the point in time when the property is no longer in negative equity then you will consent to the sale so that he will not have to incur the expense and stress of instructing a solicitor to prepare the application to Court and having a hearing.
Hopefully he will see the logic of this way forward for you both but the basic position is that he can make an application to Court for an order for sale.
Sorry it could not be better news.
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