hmmmmm. Odin did say Thor was his first born..
Well, that is a problem, if they decide to follow this line, it is only logical to make him Odin’s brother and I really like elizah72’s idea to parallel their relationship with Thor and Loki’s. I think that’s the reason they eliminated Balder from the movies, to emphasize Thor-Loki line, and now introducing another brother is like ????
Unless there is logical explanation why Tyr is older and not first in line for the throne
This is from the marvel wiki about Tyr
Later, a new god named Thor was born and became the new defender of Asgard, replacing Tyr in that role. Tyr has been resentful since. He distanced himself from his fellow gods only appearing when Asgard was in danger. His presence came to be seen as a sign that battle and the chance for glory were near.
So Tyr still could be Thor and Loki’s brother, rejected by Odin for some reason, hmm… who is his mother? Wiki says Saga, I never heard about her, maybe Tyr is older but Odin’s bastard son, and line “my first born” means first born by rightful queen Frigga, because in MCU they never mentioned that Frigga is not Thor’s real mother, making it only worse for Loki. And Loki was adopted, but it seems no one knew about this, so he is second in line coz everyone think he is Odin and Frigga’s son,king and queen of Asgard.
Plus, Odin never intended to make anyone his successor except Thor
So Tyr might team up with Loki, not coz he likes him, but because he doesn’t like Thor. And he is God of War, so no sentiments here, he actually might not even see why the heck to punish Loki for attempt to conquer Midgard.