Preheat the oven to 350°F (175°C). Lightly grease your loaf pan or line it with parchment paper for easy removal.
In a mixing bowl, mash the sweet potatoes until smooth, and then add the mashed bananas. Combine well.
Stir in the melted coconut oil, brown sugar, and granulated sugar. Mix until fully incorporated.
Add the eggs and vanilla extract to the mixture and whisk until smooth.
In a separate bowl, combine the baking soda, baking powder, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. Be careful not to overmix.
Pour the batter into the prepared loaf pan, smoothing out the top with a spatula.
Bake in the preheated oven for 60 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and let the bread cool in the pan for about 10 minutes. Then, transfer to a wire rack to cool completely before slicing.