The revocation of power of attorney deed can be made by issuing a registered notice to the power agent by all those or even one of the principals.
Their authority to act continues until the power of attorney is revoked (i.e. cancelled). In power of attorney terms, the person who grants (and can revoke) the power of attorney is referred to as the 'Donor' and the person (or persons) who acts on their behalf is known as the 'Attorney'.
Despite its name, an irrevocable power of attorney can be revoked in some situations. If the agent or attorney-in-fact is abusing his position by acting in a manner contrary to the best interests of the principal, a court action can be filed to revoke the power.Provide your Attorney with the notice they are entitled to if you decide to revoke or cancel their appointment with this deed of revocation.
Until and unless your mother and her sisters have not executed a registered release deed, the relinquishment that they have reportedly made long ago shall not be valid, they can claim their share in the properties even now.