Remove seeds from orange and lemon halves; coarsely chop rind and pulp.
Pulse orange, lemon, and grapefruit in a food processor 8 to 10 times or until the fruit is finely chopped.
Cook chopped fruit and remaining ingredients in a heavy saucepan over medium heat, stirring constantly, until sugar dissolves. Cook, stirring often, until a candy thermometer registers 220°.
Pack mixture into hot sterilized jars, filling to 1/4 inch from top. Remove air bubbles; wipe jar rims. Cover at once with metal lids, and screw on bands.
Process in boiling-water bath 5 minutes.
This is fabulous. Tart and sweet all at the same time and oh so easy to make. It's become an Easter gift giving tradition at my house.