Mobile Suit Gundam: The Origin, Vinland Saga Recommendations
Both Thorfinn and Casval serve the murderers of their fathers, making a name for themselves as skilled merciless warriors on the battlefield in the hopes of an opportunity to take revenge upon their own leaders.
There are differences in their upbringing however, Thorfinn lived humbly with a fairly average family under a caring warrior father. We see his childhood as having fun, enjoying a naive conception of fighting and war.
Casval, on other hand, is somewhat of a noble, raised by a politician with a messiah complex.
Historical setting and Space opera heavy on war drama. Protagonists start as kids who, as a result of certain similar event, develope an interesting talent for war in their teen years and polish them for purpose of revenge.
Revenge! It is the topic when starting the plot. Both protagonists will do whatever it takes to fulfill their objective, regardless of joining the side that has hurt them so much.
Both present powerful protagonists (in their field) in addition to great battles. Plus: They also present their dose of ....Betrayal!!!.