2 Syllables: SU
almond, common, Compton, conference, conscience, constant, convent, Johnson, Johnson's, Johnston, Jonson, Longman, omnium, quantum, Taunton, Thompson, Thompson's, Thomson, Thomson's, wanton
3 Syllables: USU
despondent, inconstant, preponderance, remonstrance, respondent, uncommon, Wisconsin
4 Syllables: UUSU
correspondence, correspondent

Found 29 words across 3 groupings. Skipped 6 excess words of a similar stem.