Finally, I can think of her name.
1. Younger sister : her name is Ayase, Age 14 year old. ( Blond hair )
2. Sister : her name is Chitose, Age 16 year old.
3.Oldest sister : her name is Elise, Age 18 year old. ( Blue hair )
But, their information. I have not thought
Do not doubt, why Chitose is the eldest of Ayase ?
Because i like sister Loli model hehe
thanks you ^_^