Kevin was elected to parliament in June 2001, representing the constituency of Cardiff West. In 2004, Kevin was appointed as PPS to the chancellor of the Duchy of Lancaster, Alan Milburn. After the 2005 general election, he became a junior whip in the Government Whips Office, and in 2006, was promoted to Lords Commissioner to the Treasury, a senior government whip position. In June 2007, Kevin was appointed to the Department for Children, Schools and Families as minister for young people and families.
Kevin was also the chairman and founding member of the All-Party Parliamentary Group on muscular dystrophy. The group aims to bring together parliamentarians, scientists, muscular dystrophy charities and campaigners in an attempt to raise public awareness of muscular dystrophy and find a cure for all forms of dystrophy. He was named ePolitix Disability Charity Champion 2005 for his work on muscular dystrophy.