How can we give up our share in ancestral property to brother/sister?

Your husband needs to execute a relinquishment deed.

Relinquishment deed is a legal document/instrument where a person legally or formally gives up or releases his legal rights of the said property being relinquished in the name of some other person.

If a property has joint owners, for example Hindu joint family property, one joint owner may give up his/her rights over the property in favor of another. This is referred to as a release/relinquishment. 

It is a transaction that is similar to a transfer and amounts to a transfer. : 

A release of rights in immovable property should be by a written deed and registered. The registration takes place in the office of the Registrar within whose jurisdiction [the area over which the Registrar exercises his/her authority] the property is situated.

Procedure: Stamp duty must be paid as per the laws of your state, depending on the value of the property and you can even get the document registered.

You can also do gift deed in case few stares do not recognize relinquishment deed but you have to pay exorbitant court fees on the same.

Kindly contact us for any further details and action.