Complex sentence: It is not a formal political body and is not the same as the former Great Council of Chiefs, which was a political body with a prescribed constitutional role, although the membership of the two bodies did overlap to a great extent.
Split into simpler sentences: It is not a formal political body and should not be confused with the former Great Council of Chiefs, which was a political body with a prescribed constitutional role. The membership of the two bodies did, however, overlap to a great extent.