Totally agree with Yustaf. Your army kills someone, especially in a sneak attack war started due to greed, then you should expect your life to be forfeited.
Also, yeahhhh this is not incest at all. If this is incest marrying your childhood friend/school first love is too cause you’ve known each other too long. Critical thinking is important, look at their relationship and closeness throughout their lives. A lot of kids are basically raised together (close family friendships, sleep over every other night, etc) but you wouldn’t call that incest. It’s kind of hurtful and weird to think of everything in a box like this since there are people out there that grew up close to their spouse but have done absolutely nothing wrong.
On top of that fiction can do whatever it wants as long as people can continue to differentiate it from reality, which goes back to learning critical thinking.