Another unit was added on to the communal dwelling each time a marriage created a new family.
( ( ( Another unit ) ( was ( ( added ( on ( to ( the ( communal dwelling ) ) ) ) ) ( each time ) ) ) ) ( ( a marriage ) ( ( created ( a ( new family ) ) ) . ) ) )
(ROOT (S (S (NP (DT Another) (NN unit)) (VP (VBD was) (VP (VBN added) (PP (IN on) (PP (TO to) (NP (DT the) (JJ communal) (NN dwelling)))) (NP (DT each) (NN time))))) (NP (DT a) (NN marriage)) (VP (VBD created) (NP (DT a) (JJ new) (NN family))) (. .)))
Nothing happens when a marriage creates a new family.
( Nothing ( ( happens ( when ( ( a marriage ) ( creates ( a ( new family ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Nothing)) (VP (VBZ happens) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (NN marriage)) (VP (VBZ creates) (NP (DT a) (JJ new) (NN family)))))) (. .)))