In Madeleine L'Engle
's A Wrinkle in Time
series, Charles Wallace (who never, ever goes by Charlie, Chuck, or any other nickname
) is Meg Murry
's extraordinarily intelligent kid brother. The son of a biologist mother and a father who does secret work for the government, Charles Wallace is small, straightforward (though shy) and often picked on at school, by both bullies and
the forces of darkness
At one point, Meg must travel inside his body at a infitesimally microscopic level to fight the evil powers that wish to destroy him. Later on in the series, Charles Wallace appears in A Wind in the Door, as a central character along with Meg and Calvin O'Keefe, the next-door neighbor.