Third-party pov
He had no reason to stay in the family anymore, even if he wanted to, he had no binds here. He had nothing that could keep him here.
Alexander was gone. The one person who understood him even more than he understood himself were gone. And even though they had had their turfs, they always ended up making up. Amelia was also gone, which meant that he really had no particular reason to keep staying in the garner household.
If Jia really needed someone to spy on the garner household, she would need to look for someone else, because Ryan was leaving.
He made up his mind.
Staying in this house would just bring him bad memories. Granted the garners had saved him more than one and it would kinda feel like a betrayal if he left, but he had to do this. If not for himself but for the family. He would just be the reminder that their son was no more.