Radin is the longest-serving Member of Parliament in Croatian history, with a service lasting 32 years, 156 days, as of 10 February 2025.

Although he is formally an independent, he has closely cooperated with the liberal regionalist Istrian Democratic Assembly party, in whose parliamentary club he also sits.

He earned a degree in psychology from the Faculty of Humanities and Social Sciences in Zagreb and later gained a PhD in the same field of study.

Radin is married to sociologist Helena Štimac who is chairwoman of the Office for Gender Equality of the Croatian Government.

His brother Fabrizio, a member of the Istrian Democratic Assembly party, is the president of the Executive Committee of the Italian Union in Croatia and he was the Prefect of Istria County, from 6 July 2019 until 2021 elections.