Mr Kerin was born in Bowral, NSW and was educated at Hurlstone Agricultural High School, Bowral High School, Picton Evening College and the Australian National University.
 
Mr Kerin was first elected to the seat of Macarthur in 1972 but lost the seat in the election of 1975. He then gained the seat of Werriwa in a by-election in 1978. He became a member of the Shadow Ministry in 1980 as Spokesman on Primary Industry.
 
On the election of the Labor Government in 1983 Mr Kerin became the Minister for Primary Industry and later Primary Industries and Energy. Mr Kerin held these positions until 1991 when he became Treasurer. Later the same year Mr Kerin transferred to the portfolio of Transport and Communication. This position was of a short duration before Mr Kerin became Minister for Trade and Overseas Development. Mr Kerin held this position until shortly before his resignation from Parliament in 1993.