It's common to wonder why your ears or your child's ears stick out when others' don't. Having prominent ears is most commonly the result of cartilage overgrowth when the ears are developing. The conchal bowl, which is the sunken part of the ear that you see when you look from the front or the side, is made primarily of cartilage. When there is too much, the ear pushes away from the side of the head. So, it isn't that the ears themselves are bigger, just that there is cartilage making them stand out too far.
Excess cartilage in the conchal bowl is only one reason ears may stick out. The other is the underdevelopment of the helical rim of the ear. This is the ridge that's located just inside the rim of the upper, outer ear. If this piece of tissue is not fully developed, the result may be that the upper ear sticks out or even folds forward slightly.