from  RyokoNoKalo here is the youngest brother of the royal family, Prince Alo.

Alo, the youngest brother of Amor, Hania, Maku, and Anpaytoo, is a unique merwolf prince of King Neptune and Queen Anahita; he was born blind. Both Neptune and Anahita care greatly for their blind son as well as his older brothers and sister despite him rarely leaving the palace grounds unless he is with his family on important visits to another kingdom. Even though he couldn't go out like his older sibling, he still finding ways of getting around with help from his family and the Royal Mage. When he was a child, his siblings have gotten him an eel that he named Zell to be his seeing eyes and stick close to him to help him navigate around places which the two has be inseparable since they first met. Cove, the Royal Mage, approaches King Neptune and Queen Anahita about giving him magical training in sensing aura to help him even more, which they approve and soon Alo was training with the merdragon on being able to sense aura.

Alo might be the youngest and blind, but that doesn't stop him from enjoying life and hopeful that one day he can venture off the places his siblings been going to meet and even sense what make the other parts of the seas unique like him.