Sibling relationships in Run Away are portrayed as sources of both profound loyalty and devastating harm. Through this recurring motif, Coben shows that brothers and sisters shape one another’s identities and destinies in ways that parents often can’t fully understand or control. The bonds between biological siblings and half-siblings in the novel reinforce the idea that family connections remain powerful even when hidden or fractured.

The relationship between Paige and her younger brother, Sam, illustrates both the protective instinct that often exists between siblings and the unintended consequences of misplaced loyalty. Paige, driven by the desperation of addiction, stole laptops and wallets from Sam and his college roommate to obtain drug money, but Sam conceals the theft from Simon and Ingrid rather than exposing his sister’s actions. His silence stems from compassion for Paige, yet this protection proves counterproductive. Because Simon and Ingrid never learn how severely addiction has compromised Paige’s judgment, they remain unaware of the true extent of her dependence and the immediate danger she faces. Sam’s attempt to protect his sister therefore delays the intervention she needs, illustrating that genuine love sometimes requires painful honesty rather than secrecy. Coben suggests that family members who conceal uncomfortable truths may unintentionally become participants in the very cycles they hope to prevent.

The novel also presents a darker example of sibling influence through Paige’s half-brother, Aaron. Whereas Sam represents protective devotion, Aaron embodies destructive loyalty shaped by violence, trauma, and criminality. Their biological connection immediately complicates Paige’s understanding of her own identity, revealing that hidden family relationships can exert enormous influence long before they’re consciously acknowledged. Aaron introduced Paige to heroin, effectively catalyzing the addiction that has destroyed her former life and drives much of the novel’s central conflict. His actions demonstrate how siblings can become agents of corruption and codependence as readily as they can be sources of support. At the same time, Aaron’s relationship with Paige resists simplistic categorization because his protectiveness of her is genuine, however distorted its expression. After learning that Paige had been sexually assaulted, he responded with explosive violence, brutally attacking her rapist in an act of vigilante justice. His contradictory behavior suggests that love, when filtered through trauma and criminality, can become possessive and destructive. 

The significance of Aaron and Paige’s relationship is further underscored by the novel’s revelation that the victims of seemingly unrelated murders are half-siblings. This genetic discovery underscores the inescapable pull of biological relationships. Long-buried secrets eventually surface through blood ties that can’t remain concealed indefinitely, reinforcing Coben's recurring idea that family history continually shapes the present.