Property

First joint owners who purchase the property can not relinquish their rights to each other; Relinquishment is accepted in/ among coparceners of ancestral property. Your brother can gift his share to you or on the basis of 100% payments made by you; you can get a declaratory order from the court that this property is owned by you solely, where your brother is having no objection to that but it will attract court fee as to the value of the flat.

In Uttar Prades relinquishment deeds are honoured and there is no objection to it if these are pertaining to the ancestral properties.

Once the property is in the custody of the Bank by way of mortgage, you or your brother cannot relinquish the property to the other.  You have to wait untill the whole amount is repaid to the Bank.  Or you have to pay the balance due to the bank in one payment.  After that you can relinquish.