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He was born some time between the end of "Lay Down Your Burdens, Part II" (c. day 680) and "Battlestar Galactica: The Resistance, Part I" (c. day 727), and is dedicated to the service of Ares and Apollo (Battlestar Galactica: The Resistance, Part X).
When Cally finds out that her husband is a Cylon, she attempts to kill herself and her son. However, Tory Foster, under the guise of dissuading her from her actions, takes Nicholas into her arms, only to space Cally herself (The Ties That Bind).
Following the days after they leave Earth, Galen Tyrol rushes into sickbay with Nicholas telling them he is "peeing blood" (A Disquiet Follows My Soul). Nurse Ishay and Dr. Cottle inform Galen Tyrol that his son is suffering from early renal failure but that treatment should prevent a damaged kidney. Things get more complicated when Cottle says that they have enough of Nicky's bloodtype in the bank, but Tyrol reminds the medical team that his child is half-Cylon and would need a transfusion from Tyrol. Ishay tries to tell Cottle to inform Tyrol of something important, only to be dismissed by Cottle. Cottle then proceeds to tell Tyrol privately that his late wife, Cally Tyrol, hid a secret: little Nicky is not Galen's biological child. Tyrol asks who the father is, but Cottle angrily declines that request until he can tell the birth father himself. Later, Galen Tyrol and the biological father, Brendan Costanza, erupt into a fist fight at one of Gaius Baltar's services.
Later back in sickbay Nicholas is asleep in a hospital bed while Tyrol instructs Costanza on the very basics of being a father, then turns and leaves him to tend to his son. When Costanza asks how long he must sit at Nicky's bedside, Tyrol answers, "Until I get back. That'll be after I sober up."
Nicholas was conceived before Cally got married to Galen Tyrol .
Nicholas is with his biological father when Costanza collects the pictures off of Galactica's Memorial Wall and explains it to Admiral Adama (Daybreak, Part I).
It is assumed that Costanza took custody of Nicky when Tyrol ran off to live by himself in the cold highlands of Earth.