Can married husband add his unmarried sisters name to his new property?

that is simple family settlement; If you sell the property and give the respective sahres to respective shareholders then you are free to deal with your money.

Legally your husband has no obligation to enjoin any partners in his self acquiered property but whomsoever he snjoins as partner shall be his persosnal will and moral obligations 

The facts posted as well the query lacks clarity.

What is the relevance of NOC given by the sisters? Is the mother-in-law also a party to the sale?

The gift deed was given in the name of son and wife by your father-in-law.

You are not stating the status of your mother-in-law.

The precise query was: My question is, can my husband add his unmarried sisters name to the new property which we both are planning to buy on loan jointly?

Your husband can add any names as purchasers in his sale deed and there is no law to prevent such naming of a new property.

I am afraid you are not coming out with the actual issue which is disposing of old property and not in purchasing new property.

The NOC signed by my sisters in law was regarding they don't have any objection in gifting the property to their brother. My MIL is still alive and she is the joint owner of the property currently. But in the new property, me and my husband both are planning to take loan. It's not his sole property. His unmarried sister is unemployed. 
 

Can my husband add her to our jointly owned property without my consent? And currently she is not married. In case she gets married in future then even his husband can claim the property if anything unfortunate happens to her. 
 

The old property we are planning to sell bcoz it's too small for our family and we are planning to move to the new bigger house as family extended. But the new house is purchased by me and my husband . The old property which we are planning to sell, we will only use half the amount for the new property rest we are planning to invest in capital gain bonds for his unmarried sister's future. 

More than the law, what matters is the decision of your husband. Moreover, the posting suggests deeper issues.

Dear Queriest,

From your facts I understand that you are going for jointly borrow the loan. The process of taking out a loan or other sort of finance with another individual, is known as joint borrowing. Anyone can become a co-borrower on a loan, but financial institutions do not allow just anyone to do so. In most cases, your co-borrowers are limited to your spouse or parents. Siblings may be allowed to co-borrow at some institutions. However, you should check to see if your potential lender has such a provision.

Regards,

Aryan Raj 

All the alleged owners of the plot/flat should join as co-obligants when a bank is willing to finance.  The proper way is first to enter into a  registered settlement deed for the sale of the building first between all co-sharers of deceased FIL.  The settlement should also state investment in capital bonds in lieu of her relinquishing rights.

The cash to purchase new property has two parts. One part is cash already available with the buyer  and the other part is cash borrowed from bank or any other agency. At the outset there is only part 1.  If part 1 jointly belongs to both of you concurrence of both of you is necessary to add a third party as buyer. It appears from your narration that Part 1 cash entirely belongs to your husband. The history of how the cash came into his hands is important only to the extent of whether any other person has a claim on it. For instance if a person comes into possession of cash in a bank account through nomination, the legal heirs can have a claim on it. In this case the intial cash entirely belongs to your husband only. He has the right enjoin you and/or any other person as co-purchaser for a new property. If money is borrowed to finance the purchase, all the persons on the buyer's side, whether they contribute funds or not will be jointly and severally liable to return the loan with interest..As you are not contributing any cash, your only right is to refuse to join as a co-buyer. If you are contributing cash, you can also refuse to contribute cash. Otherwise your husband is free to add any third person as co-buyer with or without contribution.