John Slattery was born and raised in Boston, Massachusetts, the son of Joan (Mulhern), a CPA, and John "Jack" Slattery, a leather merchant, both of Irish descent. John landed his first TV gig on the 1988 series The Dirty Dozen (1988) and has worked steadily since then. His television career has included the short-lived series Under Cover (1991), Homefront (1991), Maggie (1998) and Feds (1997); and the mini-series A Woman of Independent Means (1995) with Sally Field and From the Earth to the Moon (1998), in which he played Walter Mondale. By having recurring roles on Will & Grace (1998) as Will's big brother, "Sam"; Judging Amy (1999) as Amy's estranged husband; and Sex and the City (1998) as a very kinky politician, John has become one of the most in-demand character actors.