Pension income taxability?

Any one help me to clear my doubt, i allerady posted in forum but i ddnt get answer, my question is penstion received by family menbers is taxable under sec.56 and deduction is available under sec. 57 i.e Rs. 15000/- or 1/3 of such pension which ever is low. if pension is commuted, then what about tax treatmnet in the hands of legal heirs?