On the basis that the property was in your Dad's sole name, your Brother's right to remain living in there is restricted to the right granted to him under your Dad's Will. Therefore, your Brother was only entitled to remain living there rent free for a period of 5 years from the date of your Dad's death.
This right has now of course expired, and he has no further right to remain living there rent free.
I hope this answers your question and sets out the legal position.
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