Time was essence of contract 

since buyer failed to make balance payment terminate agreement and refund 50 per cent of amount received by your mother 

1. Agreement to sell is expired. File a criminal complaint in the Court of Magistrate  for trespass against the illegal occupiers. Court will direct police the  investigate, register FIR and produce the  occupiers in Court.
2. Issue notice to buyer cancelling the agreement forfeiting the  advance paid by him as he failed to comply the  terms of agreement.
3. Any one of the shareholder can take the  legal proceedings to recover joint family property.

1, If your mother is the joint owner of the property along with 5 of her children then the said agreement is in relation to only 1/6th of her share in the property.

2. Now if there is a time line within which the agreement is supposed to be completed by making the full payment and the said time is extended , then your mother can give a final extension with notice of termination if the buyer fails again.

3. if the buyer fails to pay then she can terminate the agreement , refund his money with stipulated deductions, if any and then enter in to a fresh agreement with another person.

You can serve a notice to them that the agreement is cancelled from your end for reasons known.

Your mother cannot enter into the sale agreement with the buyer for entire property.

The unregistered sale agreement is not legally valid even if the buyer approaches court to enforce the agreement

Since it is an ancestral property the sale agreement for selling the entire property by your mother without the consent and signature of the entire shareholders is illegal and invalid.

You people can issue a legal notice to your mother as well as the buyer restricting them from proceeding with the proposed sale of the property for the said reasons.

If you do not want your mother to be dragged in this legal notice then you can inform the buyer by a notice that since the agreement is expired hence stands revoked and ask him to collect the advance amount on a date fixed mutually.

Ask your mother to terminate the agreement and subject to terms of agreement forfeited the earnest money and return the balance. You can file suit for declaration against your mother, purchaser and other sisters and brothers and can assert you right in the property and to get the agreement declared null and void. Property purchased and owned by grandfather is not an ancestral property. So consult a competent lawyer before moving further. 

- As per law, an ancestral property cannot be sold without the consent of all the legal heirs , and the consent of all the legal heirs is mandatory for selling any portion of the property 

- Hence, , your mother cannot sell the entire portion of the property without taking consent of you and other siblings. 

- Further, as the  said agreement has already been expired then your mother can cancel the further transaction with the purchaser. 

- Further, you can also cancel the deal after sending a legal notice on the ground of invalid agreement ...

You can contact me if further suggestion needed. 

1. Was cancellation clause along with forfeiture clause included in the Sale Agreement  executed by your mother? Was it registered?

2. If yes, then your mother can send a letter cancelling the said agreement for non receipt of payment within the specified period. She might forfeit the amount received   if there is a forfeiture clause otherwise she shall have to return the money received by her from him.

3. Otherwise, all the children of your mother shall have to write to him stating that the said agreement is invalid since all the children of your late father are also the legal heir of the said property who were not parties to the said agreement.

4. You all can file a Declaratory Suit or Partition Suit before the Court praying for declaration that you all are the equal share holder of the said property or pray for its equal partition and in both the cases the said prospective buyer shall have to b made party.

Sir/Madam,

You have not shared as to whether you five siblings are major and whether you have given authority to mother to sell or execute agreement to sale. If Not given, then you may exercise your rights accordingly by asking the rights. Alternatively, your mother can cancel the agreement on the ground of failure/ act of other party to perform certain works befitting the spirit of the agreement. 

Dear client,

Since the agreement has expired in March 2025, and the buyer has failed to make full payment, you have strong legal grounds to cancel the agreement and reclaim the possession. Here is what you can do:

1. Send a legal notice to the buyer stating to the buyer that the agreement has been canceled and the possession must be returned to its original owner.

2. As the agreement has been done for the sale of the ancestral property, your mother alone does not have the right to sell the property without the consent of the legal heirs. So the legal heirs can challenge the validity of the sale by filing a suit for injunction in the appropriate court.

3. You can also file a complaint for the encroachment by the buyer over the property for putting the sheds on your plot.

Hope this helps you; if you still have any clarifications or issues, do not hesitate to

Proceed as per the terms of the Agreement. This means, that you can send the proposed buyer a notice through a lawyer, informing him of the forfeiture, off course in terms of the Agreement. If in terms of the Agreement, 100% of what he hard paid cannot be forfeited, make a cheque for the rest of the amount and send him the same along with the cancellation notice.