Thor had long believed his brother dead. That might have been preferable to the reality. [For this prompt on norsekink: "tl;dr- after the movie Loki falls to past-Midgard and is captured and tortured by the government. Once Thor becomes an Avenger he finds and rescues him, and nurses him back to health."]

"Let's say that Loki is Laufey's youngest, a useless runt except for how his small stature, shifting abilities and royal blood makes him perfect for a political marriage with Asgard."