From this and the other character profiles, we can estimate the character's ages.

Yui is a university student, so he's most likely no younger than 18. Moyu is stated to be 3 years younger, Kotori 5 years younger, and Fumi 7 years younger.

Kanan is Kotori's classmate, so they're probably the same age. That would make Kanan's sister, Kanon, the same age as Fumi, and those two seem to be classmates as well. Fumi and Kanon don't wear school uniforms, meaning they're in elementary school, so they're no older than 12. But if Yui is no younger than 18, then Fumi and Kanon can't be younger than 11. This gives us the following age ranges:

• Yui: 18-19
• Moyu: 15-16
• Kotori: 13-14
• Fumi: 11-12
• Kanan: 13-14
• Kanon: 11-12

Edit: Fixed Kotori's name. I misread it as "Nitori" when I first made the tag.