What happens to a property in Florida when one of its joint British owners dies without writing a will in the USA?

It's not possible to give you a final answer based on the information you have provided.  I will attempt to outline the alternatives that appear from the facts you have provided. If the real property in Florida was acquired during the period of time your mother and step-father were married, and the deed provides that they took title as husband and wife, they owned the property as tenants by the entireties, and your mother's ownership interest in the property immediately, by operation of law, passed upon your mother's death to her husband, outright.  Nothing can or need be done to change that outcome. If, however, the deed specifically provided that they took title as "tenants in common" then your mother owns a 1/2 ownership interest in the property that is subject to being disposed of in the manner set forth in your mother's will. If the property was owned by your mother and step-father when they were married, and they subsequently divorced, then the property was owned by them as tenants in common and your mother's 1/2 ownership interest should be distributed according to your mother's will. If the property was acquired by your mother and step-father before they were married, or after they were divorced, then it is probable that they owned the property as tenants in common and your mother's 1/2 ownership interest should be distributed according to her will. A review of the deed to determine exactly how the property was titled when acquired, and their marital status at the time they acquired the property, and their marital status at the time of your mother's death, can all have a bearing on the ownership rights your mother's estate may be entitled to. If your mother's interest is subject to her will, then it will be necessary to obtain an "exemplified" copy of the will from the probate court in the UK, or the original will if there was no probate in the UK, and submit it for probate in the country where the real property is located.  Through the probate process, subject to claims of creditors, and other issues associated with a probate proceeding, your mother's interest in the property, if any, will be transferred to the trustee of the trust established by your mother's will for you and your brother/step-brothers. You should contact a Florida probate attorney and provide the attorney with a copy of the deed through which your mother and step-father took title to the real property to determine what your most appropriate course of action should be. C. Randolph Coleman