One of the wife's brothers had come.
( ( One ( of ( ( the ( wife 's ) ) brothers ) ) ) ( ( had come ) . ) )
(ROOT (S (NP (NP (CD One)) (PP (IN of) (NP (NP (DT the) (NN wife) (POS 's)) (NNS brothers)))) (VP (VBD had) (VP (VBN come))) (. .)))
My brother-in-law was the only person who came to the event.
( ( My brother-in-law ) ( ( was ( ( the ( only person ) ) ( who ( came ( to ( the event ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP$ My) (NN brother-in-law)) (VP (VBD was) (NP (NP (DT the) (JJ only) (NN person)) (SBAR (WHNP (WP who)) (S (VP (VBD came) (PP (TO to) (NP (DT the) (NN event)))))))) (. .)))