That is like oromos and SomaliIt's more like Somali and Oromo; like the Oromo, the Nuer believe in absorbing and assimilating other populations; and they even make them their leaders -- once they've undergone the assimilation process.
Some Habesh were absorbed by the Nuer.
The Dinka are the only Nilotic population that don't believe in assimilating other people -- even other Nilotes; we believe that one must be born Dinka in order to be Dinka, and a Dinka with any foreign blood cannot lead us.