This "Peanuts" character got a sister named Sally in 1959
[DOC] [TLE] Charles M. Schulz, 'Peanuts' Creator, Dies at 77 - The New York Times [PAR] Feb 14, 2000 ... Charles M. Schulz, the creator of ''Peanuts,'' the tender and sage ... Sally, Charlie 
Brown's romantic little sister; Schroeder, a virtuoso on the .... And he called 
Snoopy ''a typical Christian,'' a flawed character who is .... As Mr. Schulz got older 
he began to think about the end of his strip.