Complex sentence: The Okanagan Tribal Alliance, however, also incorporates the American branch of the Okanagans, who are part of the Confederated Tribes of the Colville, a multi-tribal government in Washington state.
Split into simpler sentences: The Okanagan Tribal Alliance, however, incorporates the American branch of the Okanagan. The latter are part of the Confederated Tribes of the Colville, a multi-tribal government in Washington state.