Logan's sister, who chooses a military career path and is characterized by a cynical worldview, often clashing with Logan over their differing responses to past traumas.

Logan's boss at the GPA, involved in government operations with questionable ethics, who eventually seeks redemption and aligns himself with Logan in a crucial turning point of the plot.

Logan's mother, whose groundbreaking but devastating work on genetic modification drives much of the narrative and whose complex relationship with Logan underscores his internal struggles.

Logan's wife, providing him with emotional stability and serving as a contrast to the upheaval in his life, though not deeply explored in the novel.

Logan's daughter, who shares a love of chess with him and represents a key emotional connection and source of motivation for Logan.

Logan's partner at the GPA, initially a trusted colleague who later plays a pivotal role in the storyline, challenging Logan's commitment to his ethical principles.