He is Layla's cousin, The son of King Neptune and the brother of Nereus.
So far, Tritannus has shown to be greedy and jealous, as shown in the second episode of Season 5. He was jealous of his father choosing Nereus, his brother to be King of the ocean.
Tritannus, angry that his father chose his brother Nereus to be King of the ocean, decides to disrupt the crowning ceremony, and fights his brother. In the end, he is defeated by his father, who is very ashamed of him and sends him to the prison in Andros. There he meets the Trix.