Stephen was born in Dublin and migrated to Australia in 1989 with his family.

He has been a Chief of Staff to a number of Government Ministers in Western Australia and Victoria and worked with the Trade Union movement.

Prior to being elected to represent Western Australia’s Mining & Pastoral Region in 2013 he was the WA State Manager for Essential Media Communications.

In 2017, Stephen was elected as the Deputy Leader of the Government in the Legislative Council and was appointed as the Minister for Environment and Disability Services.

Stephen has also served as the Minister for Electoral Affairs, Minister for Mental Health, Minister for Aboriginal Affairs, Minister for Industrial Relations and Minister for Volunteering before being appointed as Minister for Emergency Services; Innovation and the Digital Economy; Science; Medical Research and Minister Assisting the Minister for State and Industry Development, Jobs and Trade in 2021.

Following the 2025 election, Stephen has been appointed as the Minister for Regional Development; Ports; Science and Innovation and the Digital Economy, Medical Research and Minister for the Kimberley. He will also take on the role as Leader of the Legislative Council.