Starting his career at Citibank in New York, Mariano Tan Jr. began working for his father's company in 1984. Today, he is the Vice Chairman of Unilab, a company co-founded by his father.  This year, he replaces his father in Forbes' list of richest people in the Philippines. With a total net worth of $420 million, Tan is the 22nd richest man in the same country.

He owns a huge stake in real estate firm Greenfield Development. Today, he sits as the President of the Fides Foundation, a non-profit organization for abandoned elderly in the country.