1. If this property was gifted by your grandfather to your paternal aunt then it becomes their own property provided the transfer was done by a registered deed.
In that case you and your mother can be considered as an unauthorised occupier of the property.
2. The concept of adverse possession is primarily based on three fundamental principles.
Firstly, competing rights of ownership between the actual owner and the person taking care of the land. Right of person taking care of the land and making highest and best use of the land will prevail over the actual title holder of the land who does not take care of the land.
Secondly, the title of the land should not be kept in abeyance for a long period of time i.e. a situation should not arise in which the title holder of the land is not own.
Thirdly, it is presumed that the actual title holder has abandoned his possessory rights if despite knowing that some other person is claiming hostile possession over his land but he chooses to keep quiet and not taking any action against the said person as provided under the law.
your possession satisfies all the above three conditions hence you can file a declaratory suit to declare your title by perfecting the law of adverse possession.
3.
The concept of adverse possession has been well settled by the judicial committee of the Privy Council in 1907 in Perry v Clissold wherein it was held :-
"It cannot be disputed that a person in possession of land in the assumed character of owner and exercising peaceably the ordinary rights of ownership has a perfectly good title against all the world but the rightful owner. And if the rightful owner does not come forward and assert his title by the process of law within the period prescribed by the provisions of the statute of Limitation applicable to the case, his right is forever extinguished and the possessory owner acquires an absolute title. "
The decisions of the Privy Council though not binding on the Supreme Court but still the said decision was upheld by three judges of the Hon’ble Supreme Court in the case of Nair Service Society v K.C. Alexander.Thus it can be said that till date it is a good law, that if a person in hostile possession of the land though not being the true owner, becomes the absolute owner if the rightful owner of the said land does not come forward within the statutory period of twelve years as provided under the Limitation Act, 1963.
4. You can challenge the eviction suit if they file one on the basis of the documentary evidences in your support and merits in your side.
5. Apart from certain provisions of the Specific Relief Act, 1963 regarding the dispossession of a person without his consent from an immovable property the provisions of Limitation Act, 1963 are relevant in the cases of adverse possession of an immovable property.
You may file a suit to declare the title to your name based on the following lines:
However there is an exception regarding extinguishment of right under the Limitation Act, 1963 as provided under Section 27 which provides that in case the person has not taken any action for recovery of possession during the period of limitation then his rights get extinguished. So in a situation where a person does not take any action for recovery of possession of land within a period of twelve years as provided under Article 65 in Schedule I of the Limitation Act, 1963 his rights get extinguished and therefore the land is left in abeyance. But the law of adverse possession is based upon the principle that a land cannot be left in abeyance for a long time as already stated above. Hence someone has to be the owner of the land when the rightful owner has lost his rights once failed to take action as provided Section 27 of the Limitation Act. So in the said situation the person is adverse possession of the land becomes the rightful and absolute owner of the land as per Article 65.