Wife Marian Heffernan [nee Andrews], son Cathal, and daughter Megan from an earlier relationship.
Togher AC, Cork, IRL
Liam O'Reilly (POL) (robandmarianheffernan.com, 25 Nov 2011)
His wife Marian Heffernan is also an athlete, representing Ireland in the 400m. (independent.ie, 14 Feb 2012; irishtimes.com, 05 Oct 2011)