You have a lot of options from his family, do you like any options from yours? That would sway my vote a bit probably.
I like Kian Thomas, Kian Louis, Kian Sinclair or Kian Edward the best. I dislike any of the names ending in -n since Kian ends in -n. This isn't a dealbreaker if the MN ends in -n that you like the best, but since you have such a long list I had to start eliminating somehow! I also dislike, Darius, Corey, Asa, Caelum, Cleveland, or Talat, whether its because of flow or just NMS. I guess since Kian isn't a common name, I like the option of giving him a more traditional MN but that's JMO.