In episode three, viewers are introduced to Susannah's half-sister Aunt Julia (Kyra Sedgwick) and Conrad and Jeremiah's cousin Skye (Elsie Fisher) after Belly and the boys learn that Julia is selling the Cousins Beach house. The distant and cold Julia and Skye, who identifies as non-binary, are characters created for the TV series, helping to raise the stakes and tension.
"I think I was daunted by the concept when I first heard about it, but that diminished the second I got there," Sedgwick told E! News of joining the cast. "Everyone was so lovely." It also helped having Elsie by her side, with Kyra adding, "We had each other to bond and be the new kids on the block."
For Han, Julia and Skye helped to fill a storytelling void left by Susannah's death.
"So much of the story of The Summer I Turned Pretty is about mothers and children and the world of Cousins," Han explained to Entertainment Weekly. "In losing Susannah, we kind of wanted to take the opportunity to gain another mother-and-child relationship. Bringing Aunt Julia and Skye into the world, that was our opportunity to do so, and also to get a glimpse into Susannah's history and one more look back on who she was and where she comes from."