Or search: progeny, firstborn
2 Syllables: SU
deadliest, Eliot, Eliot's, Elliot, Elliott, helmet, helpless, jealous, pelvis, selfless, trellis, velvet, wealthiest, zealous
3 Syllables: USU
Marcellus, rebellious, umbrellas

Found 17 words across 2 groupings. Skipped 1 excess word of a similar stem.