He was brother of Hugo Jr (1933–1976), Elisabeth Silfverstolpe (1935–1985) and the former Swedish Minister for Foreign Affairs, Margaretha af Ugglas.
He passed the studentexamen at Östra Real in Stockholm and received a Candidate of Law degree from Uppsala University and a Master of Business Administration degree from Harvard Business School in United States in 1970[4] together with Endre Røsjø.
After Harvard, Stenbeck went to work for Morgan Stanley & Co Inc. in New York City from 1970 to 1976[5] and then his career in business continued with the formation of the mobile phone company Millicom.
Control of the Kinnevik Group was passed to his daughter Cristina Stenbeck after his death of a heart attack.
[6] On 22 December 1976 in Glen Head, New York, Stenbeck married Merrill MacLeod (1944–2006), the daughter of the editor and the publicist Robert Fredric McLeod and Caroly (née Waring).