Xavier Rubiralta

Xavier Rubiralta owes his fortune to Spain-based Werfen, a diagnostics company that specializes in hemostasis, acute care, transfusion, autoimmunity and transplants.

A member of Werfen's board since 2013, he inherited his stake in the company from his late father in 2012.

Werfen's roots stem from his father and uncle who founded the business in 1966 as a health products distributor; it went on to acquire U.S.-based Instrumentation Laboratory in 1991.

Each inheriting equal stakes from his father, his brother Jordi, Jose Luis and Marc are also billionaires.