Willie is married to Kay and they have four children, Deborah, Mark, Lorraine and Ian, and two grandchildren. Willie is a native of Naas. Educated by the Christian Brothers in the town and later studied at the College of Technology in Bolton Street. 

Has been a member of Naas Town Council since 1988 and has been elected at each subsequent election. Son of the late Bill Callaghan, who served on both Kildare County Council and Naas Town Council. 

Willie is a member of Kildare County Council since 2003. He has been a member of Naas Town Council for the past 21 years and was the first Mayor of Naas.

He has a good knowledge of local government, 

Willie is known as a hard working Councillor and this is visible in the various committees of which he is a member, both locally and nationally.

He is a Peace Commissioner, a member of Naas Town Council's Protocol, Twinning Finance and Garda Liaison Committees, member of KCC Protocol, Transport SPC committee, also a member of Co. Kildare VEC, Chairman of Board of Management of St. Patrick's College in Naas, Director of Kildare Community Partnership and National Treasurer of the Municipal Authority of Ireland. The Minister for the Environment and Local Government appointed him as a member of the Environmental Protection Agency Advisory Committee.

 
He is also well known for his community work throughout the area as the coordinator for the Blood Transfusion Services and the Organiser of the Easter Parade for the past 18 years. 

He has a keen interest in sport; Horse Racing, GAA, Rugby, Golf.