who is jack harkness?
He is a fictional character  in "Doctor Who" and its spin-off series, "Torchwood".
Jack Harkness
Captain Jack Harkness is a fictional character played by John Barrowman in "Doctor Who" and its spin-off series, "Torchwood".
who does jack end up with in secret life UNANSWERABLE
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Jack Harkness [SEP] Introduction
Captain Jack Harkness is a fictional character played by John Barrowman in "Doctor Who" and its spin-off series, "Torchwood". The character first appears in the 2005 "Doctor Who" episode "The Empty Child" and subsequently features in the remaining episodes of the first series (2005) as a companion to the series' protagonist, The Doctor. Subsequent to this, Jack became the central character in the adult-themed "Torchwood", which aired from 2006 to 2011. Barrowman reprised the role for guest appearances in "Doctor Who" in its third and fourth series, the two-part special "The End of Time" and the twelfth series episode "Fugitive of the Judoon".