Wife need to file partition suit.

See your wife can wife for succession certificate and can give notice to sister in law and minor kids to produce the documents through court.

The succession certificate is for the FD and movable assets for the property you need to file for letter of administration.

Dear Sir,

Immediately file suit for partition and get stay order not to disburse the FD amounts and not to alienate other properties thus you can leisurely fight and get 50% share.

succession certificate is only for movable debts and securities

2) issue legal notice to daughter in law to furnish details of FD , bank deposits , investments lying in her possession 

3) your wife should file suit for partition for division of properties , bank fixed deposits 

4)mention that  sister in law has failed to disclose these details . seek court orders to direct SIL to furnish said details 

On demise of father in law,  your wife entitled to claim equal share. Your wife should file partition suit at jurisdiction civil court and mention about all fds and other assets. 

1. First of all, why are you so much interested? You wife inherits from her father; not you from your father in law.. Tell me whether your wife is interested in claiming her share? It's she who is entitled to take legal action; not you. Any steps taken by you won't stand judicial scrutiny, and let's make no bones about it, it will be waste of time, efforts and resources for you. 
2. So encourage your wife to think of claiming her inheritance, rather​ than trying to captain yourself everywhere. Once she's prepared to.fight legal Battle against her sister-in-law (if need be), then she can seek advice

you can file partition sit in that case. Also in succession court can direct her to submit the documents from her custody.

Your wife will have to file letters of administration and a partition suit to claim her 50% share

Hello, 

File a suit in the civil court with a prayer that the original are in custody of the daughter in law and she be directed to present the same before the court during the course of the proceedings. 

Send a legal notice to her before filing the case in the court of law. 

Regards 

First ask your wife to issue a legal notice to her sister in law seeking her half share in all the properties whether immovable or movable that belonged to her deceased father.

The legal notice copy may be served on the bank manager asking him to stop disbursement of the FD amount to her till a decision is arrived from a court of law with regard to the successors in interest to avail the claim amount accordingly.

After that she may apply for a legal heirship certificate through the revenue department for the immovable proeprty and succession certificate through court of law for the movable properties.

She can mention in her petition that the original FDRs are held by her hence she may be directed to produce the same before court for verification.

You may discuss with your advocate on all such further issues.

1. The property and bank money, everything is lying without any Will executed by the owner of the property.
2. All would be needed legal heir certificate from the Tehsildaar office as this would be needed to divide the bank money.
3. Then succession certificate from the court of law to claim share in the property (immovable).
4. Anyone can file a suit for share in north he properties, and then there would be stay from creating any third party interest or taking without following the due process of law till the final outcome of the suit.