Gyllenhaal channeled the tight bond he has with the two daughters of his older sister, actress Maggie Gyllenhaal – Ramona, 8, and Gloria, 3.
"I have two nieces whom I adore and whom I'm connected with in so many powerful ways," the actor told PEOPLE in this week's issue. "They are deeply ingrained in the movie, and my love for them is there."
While the 34-year-old actor has not been able to add "father" to his résumé offscreen, it's something he looks forward to in the years to come. "I would love for it to not be fictional," he said.
Gyllenhaal is currently single, and despite past high-profile relationships with Kirsten Dunst, Reese Witherspoon and Taylor Swift, he denies rumors that he's dating his Southpaw costar Rachel McAdams.
But the actor admits he encounters his share of intriguing people at work. "There are these extraordinarily charismatic people in the entertainment industry, it's hugely intoxicating," he said. "It can be distracting from your creativity."
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For much more from Jake Gyllenhaal, pick up the latest issue of PEOPLE, on newsstands Friday