"He's trying to be a good guy in the situation. He still has love for the girl -- it's just his schedule and life did not fit in with having a relationship," an insider told the magazine this week.
"She is 5 1/2 months pregnant now, but they are not dating," the New York Daily News quoted a source as saying. "His friends know about it, he is doing the right thing and will be taking care of her and his baby financially."
Hirsch, 28, is best known for his work in the films "Milk," "Into the Wild" and "Alpha Dogs." He lives in California.
UsMagazine.com and the Daily News did not identify the mother of his child other than to say she is from Florida.
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