Jason Patric: 'I'll Fight 'Til I'm Dead' to See Son

Aug. 16, 2013 — -- Jason Patric is best known as the star of "The Lost Boys," a prince of Hollywood who has dated some of the most glamorous starlets of the past two decades.

But it's his role as a father that has most recently launched public scrutiny into some of the most private aspects of his life.

Watch the full story on "20/20: Famous Parents, Famous Problems" TONIGHT at 10 p.m. ET.

The trouble began three years ago, when his former girlfriend, Danielle Schreiber, asked him to help conceive a baby.

"I've been in a lot of relationships," Patric said in an interview with "20/20" anchor David Muir. "I was always worried about having a child. ... But I was with someone, and I was at a certain age, [with] someone that I trusted and I loved. And so I said, 'Well, we can try this route.'"

A year later, their son, Gus, was born through the miracle of in vitro fertilization.

For the next two years, Patric said, he was at the house every day.

"Absolutely," he said. "I play music. I scratch his back. I help him articulate his fingers. I speak Shakespeare into his ear, 'cause I think that he should know that one day."

But while the love for his son only grew, the relationship between Patric and Schreiber grew strained.

Patric had every intention that his parenting relationship with Gus would continue, he said.

"Of course. I mean, it's not just me," Patric said. "The two most important words in a child -- the two most important visions, ideas -- are Mama and Dada. It means safety, support, food, love. That's there. I mean, that was always going to be the case."But, Patric said, when he filed for joint custody, he discovered something shocking.

"My lawyer said to me, 'They're saying you're not the father.' And I said, 'What?'" Patric said, laughing. "'You're not the father.'"In California, a sperm donor has no paternity rights. Without a marriage or a written agreement with Schreiber, Patric was not the father in the eyes of the state.

Asked if he ever said he would help but didn't want to be the child's father, Patric said, "No."

He never would have agreed to participate in IVF had he known Schreiber might not have wanted him to be the father, he added."I was going to be the 'intended parent,' as that says [on the IVF forms, which Patric brought to the interview]," he said. "The word parent, if you look in the dictionary, means, 'to beget birth, nourish or raise a child.' And that was my intention."

Patric provided videos showing him in a normal father role: Gus' first haircut, a birthday party, the moment when Gus recognizes Patric's photo on a Playbill.

And he recounted a Christmas card from Schreiber.

"In her handwriting," Patric read, "'Jason, I love you more than anything. What else can I say? You've done everything.' Then for Gus, 'Dada, thank you for teaching me to pee in the toilet, watch airplanes, learn Beatles songs. I love you, Dada. Gus.' There's nowhere in that card where it says, 'I love you, sperm donor.'"

But Schreiber has said Patric never intended to be a father because he insisted that his sperm donation remain anonymous.In a statement, Schreiber said, "I allowed Patric to have contact with my son while we were dating. And even then he insisted that I keep his donation a secret and uphold our original agreement."