Utilize the input text as a context reference, choose the right relationship between Commonwealth Bank and National Bank from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Westpac Corporation and ANZ Banking Group are both 21 per cent down, with Commonwealth Bank and National Bank closely behind but not in official bear mode yet.

Answer: legal_form