As the only son of a pair of explorers and scholars, Llywellyn Le (named for a fallen friend of his parents), Llywellyn Le spent the first few years of his life on expeditions with his parents. However, at the age of three, his mother and father vanished while sailing, leaving Llywellyn orphaned and with a terrible fear of the deep, blue sea. He was taken in by his maternal grandmother, and he ended up growing up in Caernarfon, Wales, where he spent most of his childhood. He also traveled a lot around the continent with his grandmother when her health allowed.

Llywellyn is a serious and practical young man with a phlegmatic nature. A stickler for details, Llywellyn often creates complicated and precise plans and schemes for everything, although he doesn't always carry them out. Raised by a traditional older lady in a privileged manner, Llwellyn can be a bit of a snob and enjoys the finer things in life. He also has impeccable manners.

Mostly unremarkable in looks, Llywellyn is of average height and figure, and he has dark hair and eyes. As a young child, he suffered a burn while playing in the kitchen, and the scars are still noticeable on his neck and part of his face. The only other notable feature of his is his lack of a right index finger. He learned that you shouldn't stick your fingers in pencil sharpeners the hard way. Otherwise, he is a rather normal-looking boy, although many of his grandmother's friends have pinched his cheeks and remarked on how plump they are. He also has a very sharp chin and even sharper elbows.