1) please clarify on what basis you say property is ancestral
2) if it was self acquired property of your grandfather on his demise your father had one third share in property
3) your uncle could have executed sale or gift deed only for his one third share in property and not entire property
4) you can file suit to set aside sale or gift deed and obtain injunction restraining sale of property by your aunt
5) it had to be filed in court having pecuniary jurisdiction in your city
6) it cannot be filed directly in high court
7) your father should also claim his one third share in said property
8) suit for setting aside sale or gift deed may take couple of years
9) your father can also file criminal complaint of cheating under section 420 of IPC against your uncle