"She is five-and-a-half months pregnant now, but they are not dating," a source says. "His friends know about it, he is doing the right thing and will be taking care of her and his baby financially."
While the Into the Wild star is not living with his baby's mother, he plans to be there for her and the child. "He will definitely be in her life and wants to be a part of the baby's life," the source adds. "He's told all his friends about it and it's fine. He plans to be in the kid's life."
On Tuesday, Hirsch cheekily tweeted about baby news, writing: "I have a baby announcement to make. I am in fact @RonanFarrow 's biological father."
The baby is due in February and Hirsch and the woman are making plans for visitation rights for the actor without legal involvement.