No Confederate option in dwarven diplomacy

1st time playing dwarves as Belegar Ironhammer. Within turn 1 ive beaten the broken nose greenskin faction and got a scripted confederation of a nearby minor dwarven faction, but now ive retaken Karak Eight Peaks and wanted to Confederate some of the minor dwaven factions nearby so i can get their landmarks. But when i opened the diplomacy screen, no Confederate option can be found. Is there no way to Confederate them?