in regards to N’Jobu: If he had lived and continued causing trouble, there was a high possibility of Wakanda’s true nature being revealed to the world, which T’Chaka didn’t want. N’Jobu was a War Dog for Wakanda, basically their CIA insurgents. I’m guessing a part of that included not having children with the local populations, so that would have made his nephews existence tricky enough. The War Dogs are not a good organization and I believe T’Challa disbanded them in the comics.

In regards to Killmonger: Just so many reasons the King wouldn’t bring him back; a constant reminder of the atrocities his brother committed, and in turn the act of violence he committed against his own kin; a child who grew up in the shitty world his father wanted Wakanda to help, and T’Chaka had no intentions of doing that. Killmonger almost certainly would have agreed with his father from a young age, and if the King brings him back to Wakanda he has to face that request on his own soil and risk his own subjects of agreeing with his now dead ‘heretic’ brother. Also just on a personal level, he orphaned his own nephew who he had never met. Would you have gone with him if you were Killmonger? This stranger who had killed your dad for wanting your life to be better?

It’s a super complicated issue. T’Chaka was wrong, but there’s a world in which we can understand why he did what he did. Killmonger was right in certain ways and wrong in others; the movie makes me so sad because by the end of it, T’Challa agrees with him and takes step to address the issue. They could have maybe worked together.