evening and hundreds of you tweeting after our "20/20" interview last night with jason patric, dealt a major setback in a controversial custody case being watched across the country. He's fighting for... See More
evening and hundreds of you tweeting after our "20/20" interview last night with jason patric, dealt a major setback in a controversial custody case being watched across the country. He's fighting for shared custody of the little boy he fathered. Tonight, here why a law on the books for decades could be his biggest hurdle. ♪ Reporter: A cherished home video of a father and a son. Jason patric was one of the young stars of "the lost boys." He came from a famous family. Jackie gleason was his grandfather. But away from the glare, jason patric was working on something else, trying to have a baby with the woman that he had been dating on and off. Someone I trusted and i loved. I said, well, we can try this route. Reporter: Even when they were separated at times, they still wanted a baby. And jason agreed to help trying. She finally got pregnantough invitro. There was no agreement that he would play the role of father. Would you have agreed even if danielle wanted you as a father? No. Reporter: A little boy called gus. You were at the house every day? Yes. I played music. I scratched his back. Speak shakespeare into his ear. Reporter: It was father's day, which also happens to be your birthday. She gave me a big cake with gus on it. Reporter: And that was the last time you were altogether? Yes. Reporter: They continued parenting together, it changed everything. And one week later, I get an e-mail, speak to my attorney. Reporter: And the court ruled in her favor. The lawyer said you're not the father. What? You're not the father. The law says -- donor. In california, if you're not married and go to a clinic like patric did, under the law you're considered only a sperm donor with no rights. As a father. Danielle also said that jason never intended to be a father. In fact, she said that he insisted that it all be kept a secret. She writes, I allowed jason to have contact with my son while we were dating. Even then he said that I enkeep his donation a secret. Show me the document where i say secret. Reporter: In fact, he points to his own home videos. He said listen to the question danielle asks her little boy? Which one is dada right there? That's right. Reporter: Just this week, testifying before california lawmakers, hoping they would change the law, that loophole, he says that labels him simply a sperm donor and not a dad to gus. Sperm donors, a word that was never spoken in my house. Reporter: But lawmakers put the debate on hold indefinitely. As we sit here, you know the number of weeks it's been. 26, sunday. Reporter:26 weeks without seeing gus. No rights to visitation. What was the last thing you said to him? The last thing I said to him was -- I picked him up and I put him in the car, and we drove back and he said I'm missing you dada. I said that's alright, I'll see you tomorrow, little man, and i have never seen him again. Now, through her attorney, danielle reiterated to abc news that jason patric never intended to be a father to her son. He expressed an interest to in providing sperm and wanted to
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