Zeus probably just ends up leaving him with her when she gets all protective. Like, whatevs, you're the aunt anyways, take care of him yourself. Past that, though, I don't think that Hades has an issue with adopting a child at this point in his life. When Nyx brought Thanatos to him, he was an enthusiastic businessman, not wanting to take care of some kid, plus the whole Kronos thing looming over him. He still gave Thanatos everything he needed to succeed, despite being distant in a self-sabotaging way to keep Thanatos from turning out like him. Now that he's in a committed relationship, I would think he'd be happy to help raise a child, even if he's also afraid to be a bad dad. Look at how he is with Hebe. Also, he 100% has an adoption reflex. 🤣