Genius Children are a special type of child found at random. They are noteworthy in that they have a natural level cap of 99, regardless of the stats of the parents. However, it doesn't seem that their stats are any higher as a result. They are identifiable by the star on their portrait, and the star around their feet in the dungeons.
There is a lot of mystery surrounding the creation of Genuises. Many players report being unable to obtain more than 3, though other accounts state that the rate of Geniuses just plummets after the first 3, instead of being reduced to 0.