You can sue your brother based on a claim that he is holding the funds in trust for you, and claim that no matter that the account or property may be in his name, the funds put into the property or account is yours. This is a well recognized type of claim. If you actually gave him cash that he put into an account in his name, this is called a " resulting trust", and you can seek a court order that he pay you the amount held in such a trust.

You can also claim a " constructive trust" , which is where you cannot perhaps point directly to cash in an account hat you paid, but to assets that he owns that you have contributed towards to help acquire the asset or helped to maintain or increase the value of the asset. This cold include paying towards housing bills for a house in his name, or contributions of your own labour such as repairs to the property. You would be able to seek compensation from him for the amount of the contributions you have made and the value of those to the property that he owns. So it is very important that you keep track of what is paid to him what is paid towards bills or repairs for his property and also your own time or "sweat equity" in as much detail as possible, as this can help to substantiate the amount owing to you.