Why can’t they kick blonde out if she isn’t even related??? I am confused. Also would ...

Correct me of im wrong but i think they stated it in the chapters that they dont cate if it's legitimate or not as long as they are competent...

i think the successor is picked through skill. it was stated in a previous chapter, disregarding their lenieage either if they are legetimate or illegetimate as long as they are seen as superior to other candidates they may be choosen as one. but as a legetimate child ofc u have an advantage but if another child overruns u then its a diff. story.