1)issue legal notice to your nephew for claiming your father share in property
2) if amicable settlment is not possible file suit for partition for division of property by metes and bounds
3) seek injunction restraining nephew from selling the property
4) nephew cannot claim averse possession .
5) The possession of one co-heir is considered, in law, as possession of all the co-heirs. When one co-heir is found to be in possession of the properties it is presumed to be one the basis of joint title. The co-heir in possession cannot render his possession adverse to the other co-heir, not in possession, merely by any secret hostile animus on his own part in derogation of the other co-heirs' title. It is a settled rule of law that as between co-heirs there must be evidence of open assertion of hostile title, coupled with exclusive possession and enjoyment by one of them to be knowledge of the other so as to constitute ouster."