Edit: forgive me, after a quick search I found a couple of good answers under this post:

https://www.reddit.com/r/AskHistorians/comments/6u93kf/what_happened_to_all_the_little_kings_when_all/

Edit 2: Automoderator bugged me so I'll give credit to /u/rejs7 for their answer as well as /u/Brickie78