The lore of 'God of War' (2018) and its sequel 'Ragnarök' is pretty deliberate about Kratos and Faye's family—they only ever mention Atreus as their son. I dug through all the in-game dialogues, artifacts, and even supplemental materials like the 'God of War: Fallen God' comic, and there’s zero hint of another child. Faye’s backstory is shrouded in mystery, but the games emphasize her bond with Kratos and Atreus as their singular focus. Even the Jötnar shrines, which reveal so much about her past, never allude to any other kids. I think if there were another child, the narrative would’ve teased it by now, especially with how much 'Ragnarök' expanded on prophecies and family legacies. Maybe in future DLC or spin-offs, but for now, it’s just the three of them—Kratos, Faye, and their boy.
That said, the way Faye’s character is woven into the story leaves room for interpretation. Her people, the Jötnar, were known for foresight, so who’s to say she didn’t have secrets? But until Santa Monica Studio confirms otherwise, Atreus is their one and only. The emotional weight of their story revolves around him, and adding another kid would’ve diluted that.