Percy mentioned his unborn half-sister to Apollo. He said that he wanted to meet his sister when she is born and be there for her when she is in need. This was also the reason he could not help Lester to turn back into Apollo.
- Estelle is a feminine given name meaning "star" that originates from the southern region of France and surrounding countries known as Occitania.
- Estelle is named after her maternal grandmother.
- As Sally Jackson has Clear Sight, the ability to see through the Mist, Estelle may inherit this ability as well.
- Given that Sally was seven months pregnant in The Hidden Oracle, which takes place in January, Estelle was probably born in or around March.
Community content is available under CC-BY-SA unless otherwise noted.