1) your father had 750 square share in the property
2) on your father demise your mother and 3 children would inherit his share
3) in partition deed your uncle should have given your family 750 sq meters
4) your names should have been mentioned in the deed
5) move court to set aside partition deed . It has to be mentioned when you became aware of partition deed
6) delay in moving court fior 20 years has to be explained .