2 Syllables: SU
barium, Belgian, Belgium, bellum, carrion, Cheltenham, clarion, Ellen, felon, Helen, Marion, melon, Nelson, Nelson's, Pelham, requiem, Selden, seldom, Sheldon, twelvemonth, variance, variant, vellum, welcome, Wesleyan
3 Syllables: SUU
anyone, anyone's, everyone, everyone's, twentyone
3 Syllables: USU
agrarian, aquarium, barbarian, Bavarian, Bulgarian, equestrian, grammarian, Hungarian, librarian, Magellan, millennium, ovarian, pedestrian, rebellion, repellent, sectarian, unwelcome
4 Syllables: UUSU
antiquarian, cerebellum, proletarian, Unitarian, vegetarian
5 Syllables: UUUSU
authoritarian, disciplinarian, egalitarian, humanitarian, totalitarian, utilitarian

Found 58 words across 5 groupings. Skipped 12 excess words of a similar stem.