Property

1.I am a muslim,belonging to a muslim family.My father(now deceased) married 2 women in his life time.Reason for second marriage was because he couldn't conceive children from the first wife,though he had 1 male child from the first marriage who is not mentally sound by birth and is till date not mentally sound.I am the first child from the second marriage. The first wife used to live in a joint family with all luxuries and satisfying lifestyle.The second wife(my mother) used to stay far away from the joint family to avoid unnecessary issues with the first wife. My father was a successful businessman,wanted to have children so they can takeover the business when he wanted to retire.He provided us with good education and morals and fulfilled his duties of being a father,he used to stay 3 days in a week with us and rest 4 days with the joint family. 2.All the property belongs to my father in which the joint family was staying and all the documents/papers are with the first wife. 3.My father had died this year due to a medical condition,now after his death the first wife and the relatives are refusing to accept me as my fathers son,claiming all the property in their name. They plan to grab all property and give us nothing :( Though they all know that I am his son.Also they are planning on selling the property little by little as it has many floors and rooms.what can i do in this case? Also i am not working as of now because i was pursuing my education,so we dont have much money to fight a case with them.on the other hand those people are getting fat rental incomes every month from my fathers property and enjoying it and can easily get a manipulative lawyers and cheat.plz advice :(