Or search: coeval, coexisting, coincident, coinciding, concurrent, synchronic, coetaneous, coexistent, synchronous, cooccurring, coincidental, simultaneous, synchronized, synchronised, contemporaneous
3 Syllables: SUU
criminal, imbecile, integral, interval, minimal, principal, principle
4 Syllables: USUU
invincible, unprincipled, unthinkable

Found 10 words across 2 groupings. Skipped 5 excess words of a similar stem.