How to cancel agreement of sale cum gpa

The agreement of sale can be cncelled  mutually by   both the parties. However if one party to agreement to sell  is dead the heirs are usually included as binding parties in agreement (read the agreement in the begining "the parties include heiers,Sucessors asigns,etc); If the parties are not defioined as such that there is no mention of heirs or succesors  etc then the agreement is not enforcebale upon them.

For GPA once the principla is dead the power of attornry expires.