First let us know how did the property devolved to your father & uncle, is it by way of WILL or Gift or through Court decree or through family settlement deed. Based on your answer, correct advice can be given. However if the property was your grand father's self-acquired property and had died intestate, then your father & uncle should have got equal share in the property. May be your grand father through WILL would have given 2 acres more to your uncle than your father or through family settlement deed the siblings would have decided that your uncle should get 2 acres more than your father. If your father is legally entitled to equal share in the property, in the absence of supporting deed, then you can challenge the same in court. Better to consult a lawyer and show him all the available documents.