Hellboy is met in the ruins of Pandemonium by Astaroth, his uncle. Hellboy asks Astaroth questions about what happened after his birth. Astaroth tells him how the other princes of Hell learned of Azzeal's gift of the Hand of Doom to his new son, and immediately summoned entities to destroy Azzeal's home and imprison him. Azzeal's last act was to send Hellboy to safety, where he was intercepted by Rasputin's summoning (see Hellboy: Seed of Destruction). Astaroth then reveals that Hellboy had two brothers and a sister, and the brothers Lusk and Gamon appear, intent on separating Hellboy from his treasured hand, and possessing it for their own. After a trecherous battle for the object of power, Astaroth, Lusk, and Gamon are suddenly consumed by Leviathan, who had a vendetta against Astaroth. Hellboy then meets the demon who aided him in his battle against Eligos. This demon reveals that somebody has slit Satan's throat, and Hellboy understands that his vision of his visit to Satan's throne was more than just a vision, and that he has inadvertantly fulfilled the destiny he sought to deny.
*Hellboy meets more of his family members, and it’s not a fond reunion, as blood sprays through the air in Hell. *Source: darkhorse.com