Combine cherries and reserved cherry juice, sugar, orange juice, lemon juice and cornstarch in medium saucepan; bring to a simmer, stirring constantly. Cook for 1 minute; remove from heat. Add butter; stir until melted. Cool and add orange and grapefruit segments. Pour filling into baking dish or pie pan.
Combine flour, sugar, baking powder and cinnamon in food processor. Add butter; pulse a few times until butter is cut into small, pea-sized pieces. Remove flour mixture from food processor; place mixture in mixing bowl. Add egg and milk; stir just until just combined; do not overmix. Drop topping mixture by tablespoons over filling until it is almost covered. Bake in a 350 degrees F oven until topping is browned and filling is bubbling and hot. Remove from oven; cool slightly before serving.