Property Rights Of Converted Person

I am Christian. My father had property, he died leaving 4 legal heirs and no will, one of them, my brother converted to Islam before my father's death. I want to know his rights on the property. Does he have rights on the property even after converting from Christianity to Islam? Which succession act will apply. He occupied the whole property and is not allowing me in or sharing any rent obtained from the property. Any help will be appreciated.