Since the author of the Negotiable Instrument died, nothing survives.

unless, one of the Legal Heir's come forward and "Renewal" such Negotiable Instrument and accepts to pay.

Note: Such renewal has to be done in writing within three years of the date of Negotiable Instrument.

Then get the Renewal/ Acknowledgement from the person who accepts it, to repay it and such Renewal/ Acknowledgement should be done at earliest earliest.. 

Also the pronote should be filled "  loan was obatained for the purpose of his Childern/legal heirs" 

Get the 'Renewal' for full money.Credit the payment of the person made in back of pronote {of what he pay} and for remaning half amount sue them it is the only way that you can claim back the amount. if not "Debt ends/dies with the death of that person"

NOTE: Pronote has validity of three years only from the date of making it, but it  may be renewed with terms and conditions

Rush to Senior lawyer at Civil Side of your area, for better details