Peel and core pears and nectarines; cut into halves and place in soaking solution to prevent darkening.
Rinse and drain.
Cook a few pears and nectarines at a time in water until heated through.
Pack hot into hot jars, leaving 1/2-inch head space.
Heat grape juice just to a boil.
Pour over fruit leaving 1/2-inch head space.
Remove air bubbles.
Process 25 minutes in boiling water bath.