Nimue
She helped protect me. My father was executed and I was too be next. I was injured, so she and Gwen looked after me, and Merlin too. Morgana also came to us twice after that.. we helped, she was just getting into her powers. She is very gifted. So, I suppose we were good friends, though I was probably like a son or nephew.
But.. umm, I'm not sure she remembers me. It's likely she could be from a point after the first meeting, when she helped hide me in the castle until I healed.