Fredrick Von Koopa is the true biological father of the 7 Koopalings, his wife being Gwendolyn Koopa. He and his wife died when the Constitutional Empire of United Creatures army burned his house down. However Bowser saved the 7 eggs and adopted them.
Fredrick Von Koopa's Father the true biological grandfather of the 7 Koopalings is three times bigger than Bowser and is most powerful.