Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.

In a large mixing bowl, mash the ripe bananas until smooth.

Add the granulated sugar, brown sugar, and melted butter to the bananas; mix well.

Incorporate eggs and vanilla extract, stirring until combined.

In another bowl, whisk together the flour, baking powder, baking soda, and salt.

Gradually add the dry ingredients to the wet mixture, stirring until just combined.

Gently fold in the fresh blueberries, being careful not to overmix.

Divide the batter evenly among the muffin cups, filling each about 2/3 full.

Bake in the preheated oven for 20-25 minutes, or until a toothpick comes out clean.

Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack.