- “I'm not going anywhere without my brother.”
- — Octavia to Indra.
Because of the one child law on the Ark, Bellamy and Octavia are the only known siblings among the Sky People. They are half-siblings.
Ever since Bellamy sided with Pike in Season Three, their relationship has been strained. After Lincoln's death, Octavia disowned Bellamy, blaming him for Lincoln's death. However, events have made Octavia overcome her own personal demons and restores her relationship with Bellamy.
Bellamy and Octavia's sibling relationship starts before the first episode of season one at Octavia's birth. After Octavia was discovered and locked up, Bellamy shot Chancellor Jaha in order to stow away on the Delinquents'drop ship so he could protect his sister on the ground. Throughout season one, Bellamy is overly protective of Octavia to the point of them getting into numerous fights. Eventually, he acknowledges his sister is stronger than he thought and in We Are Grounders (Part 2).
- Bellamy and Octavia Blake are siblings on the CW television show, The 100.
- Bellamy named Octavia. He had learned about the Roman emperor, Augustus, and named his sister after the emperor's sister, Octavia.
- Aurora, their mother, told Bellamy that Octavia was his responsibility.