My cousin's.
( ( My cousin ) ( 's . ) )
(ROOT (S (NP (PRP$ My) (NN cousin)) (VP (VBZ 's)) (. .)))
That is my cousin's.
( That ( ( is ( my ( cousin 's ) ) ) . ) )
(ROOT (S (NP (DT That)) (VP (VBZ is) (NP (PRP$ my) (NX (NNP cousin) (POS 's)))) (. .)))