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Warning! This page contains spoilers for The Ship of the Dead.
Percy mentioned his unborn half-sister to Apollo, saying that he would like to meet her.
While training with Magnus Chase, Percy mentions that he has to go back to New York and babysit his newborn baby sister.
Estelle is a female name originating from the southern region of France and surrounding countries known as Occitania. It means ''star''.
- Estelle is named after her maternal grandmother.
- As both Sally and Paul have Clear Sight, the ability to see through the Mist, it is likely that Estelle will inherit this ability as well.
- Given that Sally was seven months pregnant in Trials of Apollo which takes place in January, Estelle was probably born in March.