IN: Which person is he?
Will Smith got his son in a movie since he is the son of a famous movie actor.
OUT: his son

IN: Which person is they?
The Swiss bank freezed the accounts of a crime syndicate because they were helping law enforcement catch the criminals.
OUT: The Swiss bank

IN: Which person is he?
John fired Dave because he had too many employees.
OUT: John

IN: Which person is they?
The airline unions constantly go on strike against the airlines because they do not care for the employees.
OUT:
the airlines