Charles' sister is around his age, but has only been shown once during a flashback.

In The Slump, it is revealed that Charles would often play with her dollhouse when they were children. During Chocolate Milk, Charles asks Rosa to attend Eleanor's engagement party with him, because his sister had to cancel at the last minute.

It's unclear whether she attended her father, Lynn Boyle's, wedding to Darlene Linetti, but she was never mentioned or shown as a guest.