One of the reasons he left is because, when he was young, he discovered that he was a merman. That's one of the reasons he couldn't place a family— they got freaked out by his ability to turn into a half fish. Eventually, the attention became too much.

     As for his new family, he's actually referring to a science lab and scientists, and he didn't love them very much. So, he broke out, ran away, and he never went back.

     He found the pod he's currently in and stayed with them, adopting them as his new family, and he has grown to love them very, very much.

     Wherever they go, he goes. He's very close to them and never wants to leave them or lose them.