keep grown-ups from squirming in their seats 
(ROOT (S (VP (VB keep) (NP (VBN grown) (HYPH -) (NNS ups)) (PP (IN from) (S (VP (VBG squirming) (PP (IN in) (NP (PRP$ their) (NNS seats)))))))))
(ROOT (S (VP (VB ) (NP (VBN ) (HYPH ) (NNS )) (PP (IN ) (S (VP (VBG ) (PP (IN ) (NP (PRP$ ) (NNS )))))))))