Frigga loves them both equally, like any mother would (that Loki came from elsewhere doesn't matter after he opens his eyes and looks at her that first time). It would be wrong to say that she loves either one more. Thor is easy to dote on: all open, uncomplicated smiles and ham-fisted attempts to prove his love. Loki is…Loki is more complicated. He's always thinking, always learning, always seeking something he never seems to find, and Frigga sees herself in him so much when he asks impossible questions about the realms and the Bifrost and why Heimdall can see and hear all but no other Asgardian can. He questions everything, and he wants to know the reasons behind the rules. And somehow Frigga is able to answer him, almost all the time. Odin won't, so Frigga does, because Loki needs to know in a way Thor never seems to, and he's her son regardless of what color his skin turns when it's cold. She loves both of her sons equally, but sometimes she looks at Thor like he's a stranger, or a smaller version of her husband with no part of her involved, and sometimes she looks at Loki and sees herself and not an ounce of Odin.
—-
They are happy and laughing, and forever together, and they are playing hide-and-seek in Asgard, which is as everyone knows the best place in all the realms to play hide-and-seek. Loki is the best possible player of hide-and-seek, regardless of which role he's in at the moment: he hides everywhere and nowhere, and he (always, immediately) finds the person for which he seeks. Thor is terrible at the game, which is why they play so often. Loki always wins, and that this is the one thing he wins at is not lost on anyone; that it is prophetic is not yet known.
—-
Loki's dark hair is matted and tangled from the breeze and the playful wrestling match with his brother, who looks, as always, like a young king in golden plate. They jostle each other as they play another game: trying to sneak up on Heimdall, which is impossible but quite a lot of fun as he likes to play along sometimes. Heimdall lets them get near enough to touch, and pokes them in the bellies with a long finger, and tells them everything they've done that day. Heimdall is huge and kind and could rip them apart with his bare hands. Part of being an Asgardian is knowing that Heimdall chooses not to kill them all, and being grateful for it. The other part is knowing that Heimdall has no real interest in killing them all, and being happy that it's true. Loki keeps an eye on Heimdall for the rest of his childhood, thinking carefully about what it means.
—-
Thor is shivering with what Loki thinks must be anger, his face sharp and white in a way that sits strangely where a sunlit grin should be. "You cheated," and of course Loki cheated, doesn't Thor know anything? Honestly, sometimes he's so stupid. And Loki tries to explain, that he cheated because Thor always wins, but it's no good and his brother storms off to whine to Father about it. And the Allfather comes to Loki, later, and tells him a story about a rabbit and a tortoise, and how the tortoise didn't cheat, exactly, and Loki feels a little better. Thor forgives him soon enough, but Loki remembers the swift and sudden turn Thor made. From it he learns the truth: that Thor will turn on him in a heartbeat if he suddenly starts to win.
—-
Loki has a little crush on Sif, always has, since they were children. Nothing too serious (the equivalent of a teenage fascination for immortals), but it makes Thor angry, of course, because Loki cannot should not will not have something that Thor wants (not that Thor wants Sif, exactly, but she of course would prefer the golden boy who would be king over small, skinny, silver-tongued Loki, wouldn't anyone?). And so when Loki sees Thor kiss her, he accepts this in much the same way he's accepted everything else Thor has been and done and taken: by burying it in a tiny frost-blue box in his heart, neatly folded, tucked between the way Thor doesn't think about the effects his actions have on the family or on Asgard and the time Thor "borrowed" Loki's favorite cloak and tore it and then acted like Loki was overreacting. Loki whispers in Sif's ear — things that are mostly true, because he does like Sif, after all — about the need to be taken seriously if she ever wants to be a warrior, and what people will think if they believe that she slept her way into Thor's team. Sif never kisses Thor again, and if she never kisses Loki, either, well, it's a small price to pay.
—-
Thor doesn't mean to be the way he is. Loki knows that. It doesn't matter. Thor is brash and loud and impulsive and stupid, and Loki is the one who has to pick up after him, keep him safe, lie to the Allfather and their mother about him. Loki learns to lie to keep Thor out of trouble. This is important, and no one seems to care. All they see is the lying, not the reason for it. Loki can't quite figure out how to tell them, which is an unusual feeling for him, and when he learns what he is, it all snaps into place like Heimdall opening the Bifrost, and he resolves to never clear Thor's way again.
—-
He wasn't lying when he killed Laufey. He is the son of Odin in every way that matters. Thor may not believe him, but it's true.
—-
Yes, he lied to Thor about the Allfather. So what? Thor wasn't ready for kingship, a blind Midgardian could see that. Loki did what kings do: act in the best interests of the realm. He tells himself this over and over, and Loki is very convincing.
—-
Loki always liked Midgard. The people are so clever and so dull all at once, and their capacity for destruction and hatred makes something blue and cold flare up in his chest. He feels at home here, and with the Bifrost broken he has plenty of time.