His mortal family consisted of a dead father, a younger brother, Paul, and a mother and sister, of whom we hear little.
Louis' claim to fame is that he remains the most "human" of all the vampires throughout.
He is the father of Claudia, though not by choice, and also, later, of Madeline, Claudia's doting companion.
Louis, for the most part, turns his back on his gifts, choosing to continue his life in as mortal a fashion as he can.
He despises the taking of life and is furious when he finds out only after he has been made to take human blood that he could as easily have fed from animals.