Treatment of TDS on rent if property.

One property is in the name of mother and son. The builder was making payment after deducting TDS to both.Mother is expired now and the builder has made payment for a few months to mother's accounts after deducting TDS.

what is the process in this situation how TDS on mothers account will be claimed as ITR will not be filed in the mother's name.
If the builder makes full payment to the son his tax slab will be in higher tax liability

please advise what to do in this situation.