Question: how old are ikuto and amu?
Answer: By the end of the anime/manga Ikuto is around 18 and Amu is probably 12 or 13 (this information is taken from the Shugo Chara Wiki, which I'm not sure is exactly dependable). In the beginning of the anime/manga, Ikuto is 16 and Amu 11 (again, not sure if this is dependable information).