A Letter of Authority refers to the document (or Letter) that grants the personal representative authority to act on behalf of the estate of the person that died. Probate refers to the court procedure by which a decedent's estate gets administered after death.

Therefore it is not known that what exactly is your question, because it is not known that how your mother's name was included in the letter of authority.

Are you by anyway referring to the list of legal heirs on the petitioner's side as letter of authority?

Your mother is not a legal heir to your grandmother, hence she cannot be included as a petitioner seeking probate of your grandmother's Will.

The bank lawyer is right in mentioning that your mother not being a legal heir she cannot be added as a party to this probate especially during the lifetime of your father.

In any case the probate has been granted by court hence the probate of Will should not be a problem.

You can approach a different bank for loan.

For obtaining a rectification in the probate judgment, you may have to file a reopen petition seeking to rectify the error in the original petition by filing an amendment petition and for that purpose all the parties to the petition i.e., the defendants are to be notified by a court notice and the court will pass an order only after hearing the defendants also.

It is legal heirs who are only mentioned. Children and husband of grandmother were the only class-1 legal heir. So your mother and grandchildren of grandmother are not legal heirs of grandmother. 

Bank officer is correct 

under the will your father and you are the only beneficiaries 

your mother is not beneficiary in will 

hence LOA could not have been issued in her favour 

You have to take out miscellaneous application for rectifying the mistake made in issue of LOA 

2) 

In view of the provisions of Section 152 of the Code of Civil Procedure, 1908, the Court may correct the errors in the judgment, decree or order, arising from any accidental slip or omission. Such errors may occur in the judgment, decree or order on account of the errors in the pleadings of the parties, arising from any accidental slip or omission.

3) in such a situation, the Court may permit the amendment of the pleadings to correct the errors occurring in the pleadings and may accordingly correct the errors occurring in the judgment, decree or order.

- As per law, the application for a probate, can only be made by the executor whose name is given in the Will. 

- Further, if there are more than one executors, the probate can be granted to them together or as and when the application for probate is made.

- Further, if no executor is appointed under the Will, only a simple letter of administration is issued by the court but not a probate.

- Since, your mothers name is not mentioned in the Will ,then how she can be a party in the Probate Petition. 

- Hence, the said Probate is wrong , and hence you can move an application before the same court under section 152 of CPC for rectify the Probate. 

- Since, the probate already granted ,then there can not be requirement of other legal heirs signature or appearance before the court. 

Dear Client,

The bank officer's statement is accurate. According to the will, both you and your father are the sole beneficiaries, while your mother is not named as a beneficiary. Therefore, the Letter of Authorization (LOA) cannot be issued in her favor. To rectify this mistake in the LOA issuance, you will need to file a miscellaneous application.

Furthermore, Section 152 of the Code of Civil Procedure, 1908, allows the court to rectify errors in judgments, decrees, or orders resulting from accidental slips or omissions. Such errors can arise from mistakes in the parties' pleadings due to accidental slips or omissions.

In such a scenario, the court has the authority to permit amendments to the pleadings in order to correct any errors present in the judgment, decree, or order.

You will need the signature if he is a legal heir

First of all , what the need for LOA or probate ? Not mandatory. Letter of Administration is granted to the beneficiaries. your mother is not beneficiary in the Will. 

You have to apply in court for correction. No need of other heirs.