Can't use conquest casus belli for kingdom?

[Gui-Geek]

I am a clan government but i cannot use my Holy war for kingdom casus belli on neighbours? How? I did it everytime untill now, i have conquered the Maghreb empire and some other african kingdoms but now i need to use my holy war to target Ghana kingdom and it doesn t appear on the casus belli list....Do i need to have a least one county in the kingdom to get this casus belli? It s weird because i can use holy war to conquer Igbo benue kingdom and i don t have any county inside this one.

Edit: Oh ok i think i get it, if i want to declare war to the ruler who has the kingdom title, i need to have at least one county near his own or vassals counties de jure of the concerned kingdom.