I reread through World of Ice and Fire, and it made it fairly clear that the titles "River King", "King of the Rivers and Hills", and "King of the Trident" are essentially interchangeable.
Given that "River Kings" is by far the most common variant we've seen used (and matches the pattern of "Storm Kings", though that's just extra) I'm going to combine all three into just "River Kings", and leave the other two as stubs pointing to this page. Too much information was getting divided between them.--The Dragon Demands (talk) 18:31, November 21, 2016 (UTC)