Marvel Plagiarised themselves in Black Panther (From Thor: Ragnarok)

WARNING:Has spoilers for black panther, thor ragnarok, and avengers infinity war.
As I was watching Black Panther, something seemed eerily familiar. I had seen the entire story not long ago, in marvel's previous movie- Thor.
Black Panther: A king dies and his child has to assume the throne. His relative (cousin) comes over to take over with the goal of expanding the kingdom (Wakanda) to the greater area (Earth). The king's son, who does not have this violent philosophy has to come in and stop the imperialistic relative.
Thor: A king dies and his child has to assume the throne. His relative (sister) comes over to take over with the goal of expanding the kingdom (Asgard) to the greater area (9 Realms). The king's son, who does not have this violent philosophy has to come in and stop the imperialistic relative.
You could argue that the movies ended differently but tbh Wakanda was ruined in Avengers soooo. Also, I can't believe marvel released such similar movies right after each other. I liked both movies, but even though the stories are kind of different, such similar story lines in a single franchise released right after each other is pretty ridiculous imo.