Your brother has been misled by someone and hence he is acting like a madman. 

His opposition has no basis in the eye of law. 

The property received by your mother on the basis of this Will is her exclusive property. 

Therefore she can transfer to anyone and enjoy the sale price at her own will.

However the Probate is to be taken first for this Will from the local court. 

Will is valid and your mother is fully authorized to sell the property under section 14,15 and 16 of Hindu Succession Act 1956.

Let anyone go to the Court, they would face defeat and failure of their claims against you and your mother. 

1. Yes she can sell the house without any objection from anyone. 

2. Your brother cannot take any legal action against your mother to claim any share from property inherited by your mother through will of your father even if he takes legal action he will lose the case. 

He can't take a stay on the same as he doesn't have any right in the said house. It's in your mothers name now so let him do whatever he wants to. He will not get the stay

1. Your mother is absolute owner of the property brother has no right on property. Your mother can freely sale transfer, gift or will the property. 

Es your mother can proceed as mentuoned here.

Your mother becomes the absolute owner with clear and marketable title to the property after acquiring itby enforcing the Will written in her favor. 

Your brother nor you have any rights over the property at least not during her lifetime. 

Therefore your brother's threats to get stay against the sale of property by your mother is just a fake threat,  it is not maintainable in law. 

Hindrance will come into effect when she proceeds with the sale. There is no legal remedy to stop anyone not to knock the door of law whether he is entitled or not.   It is a matter of trial.  The sale of property take time and there is enough time for the brother to challenge the Will in the court and take stay.  Now, the whole process of sale would be in doldrum.  Earnest money taken would be sought back, etc. etc. 

Will is not required to be registered.  However, if the witnesses are in favour of mother, they can get the case decided in favour of mother. 

But the thing is how to come out of it.  If your mother enter into sale agreement with any genuine buyer, your brother definitely go to the court.  You have to go through the process of law and the thing is there should be no problem to your mother and the buyer.   

In my opinion, you may create a bogus buyer and enter into sale agreement on the face of your brother and instigate him to go to the court of law.   Once the case is initiated, it would definitely bring result and thereafter, there would be no problem in selling the property.   In litigation patience is required.  Except this, I do not find any other way which is permanent and effective.  Discuss with your mother. Good luck.

The will is valid even though it is not registered.

Regards

1. By virtue of Father's WILL, Mother becomes the absolute Title-Owner of property which is legally classified as "self acquired" due to the WILL.

2. By virtue of above, Mother is absolutely and legally entitled to Sell /Gift /Transfer /Donate /Mortgage /Whatever.... without any legal reference to ANYBODY (including her children).

3. Due to above, no Court will grant Stay orders on Sale of such Self-Acquired property.

4. However, brother is entitled to challenge the WILL, stating that will is forged or father was forced or father was mentally unfit when will was prepared, or etc....  Based on this assumptions, he may cause hindrance to sale of father property.

Your mother should apply for probate of will 

probate is judicial proof that will is genuine 

enclose affidavit of one of attesting witnesses 

if there is no contest mother would get probate in 6 months 

then apply for mutation of property in her name 

she can then sell the property 

1. Since the bequest was made in favour of your mother she is the absolute owner of property.

2. She is at liberty to sell the house.

3. If your brother is threatening to stall the sale through a suit for injunction then your mother can file a caveat in the competent civil court so that court does not grant an ex parte injunction.

4. Registration of will is not mandatory.

Mother is absolute owner by virtue of Will. Court may not grant stay because brother have no say in the property neither his consent is required for sale of property.

Registration of Will is optional. Duly attested 2 witness unregistered will is valid.

On the death of the testator, an executor of the Will or a heir of the deceased testator can apply for probate. once will probated your mother can sell without consent of your brother. 

The property belongs to your mother and she has full rights to dispose of the property. Your brother cannot do anything.

Dear Sir, 

You are suggested to get the mutation done on the name of the mother and then she will be able to sell the property without any hindrance. 

- After getting the said property from your father , now it becomes your mothers self acquired property , and hence she is having her right to transfer & sell the same to anyone without the consent of others. 

- Further , your said brother is not having any right over the same , and cannot get stay from the court if he files a case against mother. 

- Further , she can file a petition before the district judge for probate the said WILL left by your father.