Utilize the input text as a context reference, choose the right relationship between Berkshire Hathaway and Warren Buffett 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.

For example, two notable value investors operate businesses that fall into this category -- Tom Gayner at Markel and Warren Buffett at Berkshire Hathaway ( NYSE:BRK-A ) ( NYSE:BRK-B ) .

Answer: chief_executive_officer