Preheat oven to 350 degrees F. Lightly grease a jumbo muffin pan or line with jumbo muffin liners (makes 6 jumbo muffins).
In a large bowl, whisk together flour, brown sugar, baking powder, baking soda, salt, cinnamon, and pumpkin pie spice.
In a separate bowl, beat eggs, pumpkin purée, milk, oil, and mashed bananas until well combined.
Add wet ingredients to the dry ingredients and stir just until moistened — do not overmix.
In a small bowl, combine flour, brown sugar, and cinnamon. Cut in butter with a fork or fingertips until crumbly.
Divide batter evenly between the 6 jumbo muffin cups (about ¾ full).
Sprinkle the tops generously with streusel.
Place in the oven and bake for 28–32 minutes, or until a toothpick inserted in the center comes out clean.
Remove from the oven and cool in the pan for 10 minutes before transferring to a wire rack.
Mix glaze ingredients together until smooth and drizzle over cooled muffins.