Science Fiction & Fantasy Stack Exchange is a question and answer site for science fiction and fantasy enthusiasts. It only takes a minute to sign up.
Sign up to join this community
Here's one of the first dialogues between Odin and Loki in Thor: The Dark World:
Odin: All this because Loki desires a throne.
Loki: It is my birthright.
Loki's mention of birthright made no sense; because he knew he is an adopted child.
Also, if it was to birthright, Thor was elder.
So what made Loki think he should've been the future king?
"A" throne (if not Asgard's) is Loki's birthright because he is the son of Laufey, the king of the Ice Giants. He might very well feel that Odin owes him a throne (since as an adopted Asgardian he can no longer claim the throne of the Ice Giants).
Odin raised both Thor and Loki as princes of Asgard ready for the throne but knew only one of them would get that chance, it happened to be Thor.
Odin: Only one of you can ascend to the throne. But both of you, were born to be kings.
Thor
In Loki’s eyes Thor probably lost the right to the throne forever after Odin cast him out in Thor. In that case the right to the throne would have passed to him and hence why it was not his birthright: with Thor having lost that right.
Of course he also still feels like as the son of Laufey he is owed a throne as we see come out later in life when talking to Thanos.
Loki: I, Loki, Prince of Asgard, Odinson, the rightful King of Jotunheim, God of Mischief, do hereby pledge to you, my undying fidelity
