Preheat the oven to 200 degrees C. Grease muffin tins, or line with paper liners.
Muffins: 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.
Topping: In a small bowl, stir together the sugar, cinnamon and nutmeg. Brush muffins with melted butter and sprinkle with the cinnamon mixture. Cool in the muffin tins over a wire rack.