In the context of the input sentence, determine the relationship between 'Berkshire Hathaway' and 'Warren Buffett'.
Options: owned by, distribution format, chairperson, director/manager

It should come as no surprise that the most popular of these portfolios is that of renowned investor Warren Buffett , CEO of Berkshire Hathaway ( BRK.B ) and one of the richest people in the world.
chairperson