Or search: adult, bush, danewort, dean, doyen, doyenne, grownup, sambucus, senior, shrub
2 Syllables: SU
cellar, dweller, elders, ellsworth, elmer, feller, healthier, heller, helper, keller, melbourne, seller, shelter, stellar, teller, wealthier, welter
3 Syllables: USU
propeller

Found 18 words across 2 groupings. Skipped 7 excess words of a similar stem.