Fake will

If the alleged will is fake and there is no other will, then your father died intestate. If your father, uncle and aunt are the only children of your grandfather, all three have equal rights over the property. If as your aunt says your grandfather had willed all the property to his sons only, your aunt will have no rights over the property. Why should your aunt produce a fake will which denies her rights over the property? You accept the will and divide the property among the two brothers only.

Sorry I didn't clearly mentioned it earlier my aunt and uncle are husband and wife they are one family and my grandfather has only two sons. My father wanted to share the properties equally between him and uncle but my uncles family wants to have the majority of the properties that's why they are telling they have a will. 

As your father has filed a case in court and if your aunt wants to dispute it saying that there is a will in their favour, they will have to produce the will before the court. At that time your father can ask for a copy of it or even that the original has to be examined by your father or by a competent neutral authority. Where exactly is the property situated? A will, fake or real should have been attested by two witnesses. The winesses also will have to appear before the court and they will be cross-examined by your lawyer. The witnesses have to submit that they actually saw your grandfather signing the will. The two witnesses and your grandfather should have been exactly at the same place at the same time when all the three signed the document.