Preheat the oven to 400 degrees F (200 degrees C). Grease muffin tins, or line with paper liners.
In a large bowl, stir together the flour, 1/2 cup white sugar, brown sugar, baking powder and salt. In a separate bowl, mix together the eggs, milk and 1/2 cup of melted butter until well blended. Pour the wet ingredients into the dry, and mix until just blended. Fold in the blueberries and peaches. Fill muffin cups with batter.
Bake for 18 to 20 minutes in the preheated oven, or until the tops spring back when lightly touched. In a small bowl, stir together the remaining sugar, cinnamon and nutmeg. Brush muffins with remaining melted butter, and sprinkle with the cinnamon mixture. Cool in the pan over a wire rack.