Time limit to claim ancestral property

12 years from the date of knowledge of such sale of joint property and it can also be treated as a fraud as brothers are not having any rights to sell the sister's property without her knowledge and consent.  The facts are not adequate.  If the property is ancestral, the brothers might have partitioned the property with father during his life time.  In that case, the daughter can only claim 1/3 share in the property of her father alone.  Irrespective of rights litigation is not the ideal way as it may take many decades to get a settlement without certainty.

The time limit to challenge the Sale Deed is three years from the date of knowledge. Your mother has to file a Suit for Partition and also a prayer for Declaration that the Sale Deed executed by her brother in favour of the third party is null and void. As said by you if they are willing for a compromise well and good, if not file a suit without waiting any further.

How is that the property is ancestral? It could be that it is not so, if you ascertain the source of title to your grandfather.

Anyhow, on the death of the gradfather the property is jointly vested with the all the legal heirs including your mother. She cannot be excluded unless and until she volunteers to relinquish her share through a deed, duly registered.

There is no limitation in the instnt case since the property vested with all the legal heirs.

Your mother should file a suit for partition in civil Court through a local prudent lawyer where the property is located, she is entitled for an equal share with her brothers.

Donot delay any more. 

Mr. P Venu, an expert on the subject has specifically mentioned qua limitation of 12 years from the date of knowledge, which has not been contravened or nagated by any other expert implies the opinion / advise is perfect and final.