Steingrímur's father was Hermann Jónasson, another former Prime Minister. Being the son of a prominent official, Steingrímur enjoyed a relatively care-free upbringing in a country stricken by the Great Depression. As a young boy he had an exceptional proximity to Iceland's World War II politics, overhearing state affairs being discussed in his father's living room.
Education
Not wanting to follow his father's footsteps into politics, Steingrímur went to the U.S. in 1948. He received a bachelor's degree in electrical engineering from Illinois Institute of Technology in 1951 and a master's degree from Caltech in 1952.[2] After returning to his native country and experiencing troubles both in his private life and business career, he eventually entered politics in the 1960s. He was elected to the Althing (Icelandic Parliament) in 1971 for the Progressive Party, the party of his father. He became party chairman in 1979.
Steingrímur first kept a low profile in his retirement, rarely voicing his opinion of current affairs. He was however a founding member of Heimssýn, an organization opposed to Iceland's entry of the European Union, and became increasingly critical of the Progressive Party's policies. He gave public support to "The Iceland Movement", an ad hocenvironmental movement which ran (unsuccessfully) in the 2007 Althing elections, appearing in campaign advertisements on TV. As a result of these activities, he mostly lost the informal status of the Progressive party's "Grand Old Man".
In his last years Steingrímur was a well liked and respected elder statesman, and was considered as a potential candidate for the 1996 presidential elections. But he quickly declined that honour, stating his intention to retire at the age of 70. His memoirs, published in three volumes in 1998–2000, became bestsellers.
By 2007, Steingrímur had left the Progressive Party, after it had turned more to the right and he appeared in TV-ads advertising the Icelandic Movement party.[5]
Steingrímur was twice married and had six children. His youngest son, Guðmundur Steingrímsson was active in Icelandic politics between 2007 and 2016. He first ran for the Althing in the 2007 elections, for the Social Democratic Alliance. In early 2009, however, he switched sides and joined his grandfather's and father's Progressive Party and got elected. Then switched again and got elected in 2013 for his own party as a chairman, Bright Future, where he attempted to become a prime minister just like his father and grandfather.
His eldest children, John, Ellen, and Neil Hermannsson reside in the United States with their own children, all of whom have been to Iceland.