Charles is shown to have a sister called Polly. However, other than this very brief appearance, she is otherwise never featured or even mentioned again in the entire series run.
Katy Kurtzman who plays young Caroline, also played Anna Gillberg in the Season 3 episode, "The Music Box".
In the episodes Journey in the Spring: Part I (1976) and I Remember, I Remember (1978) the youngster, Charles Ingalls was well acted by
Matthew Labyorteaux. He later had character role, Albert Quinn Ingalls in the series.
Caroline tells Laura she keeps the string of beads to remember her, never to make a hasty judgement about Charles. In "for my Lady" however she already did, suspecting Charles of having an affair with the widow Elizabeth Thurman.
Caroline's youngest sister Eliza Quiner married Peter Ingalls and became the third Quiner to marry an Ingalls. Peter Ingalls was Charles Ingalls (Pa's) older brother.