Drain raspberries, reserving juice in a 1-cup measuring cup. Set raspberries aside. Add enough water to juice to measure 1 cup. In a saucepan, combine sugar and cornstarch; stir in raspberry juice mixture until smooth.
Add the strawberries. Bring to a boil over medium heat; cook and stir for 2 minutes or until thickened. Remove from heat; stir in lemon juice and raspberries. Cover and refrigerate for 30 minutes.
In six parfait glasses, layer 2 tablespoons berry sauce, one scoop of ice cream, 2-3 tablespoons sour cream, 3 tablespoons sauce and another scoop of ice cream. Drizzle with remaining sauce.