Lindsay Lohan GMA: Learned Of Half-Sister Bombshell On Air (WATCH VIDEO)

Lindsay Lohan acted surprised when asked on "Good Morning America" about her secret half-sister.

When "GMA" host Amy Robach mentioned that her father, Michael Lohan, was provided DNA proof that he had fathered a now 17-year-old daughter out of wedlock with a former mistress while married to Dina Lohan, Lindsay replied: "I didn't even hear that, so thanks for the news!"

Robach then drew a comparison between Lindsay and the troubed life of actress Elizabeth Taylor who she portrays in her next film, "Liz & Dick."

"Liz Taylor's life was out-of-control at times, and to honest, so has yours. From the moment you step out of your house, there's often times drama, there's been legal trouble. Do you think your life and career would have been different without the constant scrutiny?"

"Um.. I mean obviously yes, to a certain extent, but um, I think that everyone goes through things in life, and I like to learn from my mistakes," Lindsay answered. "I wouldn't be who I am today if I hadn't gone through certain things, everything happens for a reason, good or bad, so you can just take what you've learned from it and move forward."

Enstarz reported that Lohan has a half-sister, according to a DNA test taken Thursday on "The Trisha Goddard Show."

When Michael Lohan, 52, agreed to take a paternity test, it revealed that he is the father of 17-year-old Ashley Horn. Ashley's mother, Kristi Horn, claimed to have had a relationship with Lindsay's father more than 17 years ago while he was still married to the actress's mother Dina Lohan, according to RadarOnline.  

In a clip shown from the daytime talk show, the TV host is seen asking who wants to open the DNA results envelope. Ashley volunteered stating, "I'll do it, it's my life."

Michael then added, "It's all of our lives."

Ashley opened the envelope containing the DNA test and moments later, Kristie broke down in tears while Ashley remained silent.

Goddard leaned over to look at the results and announced "Michael is Ashley's father."

"You have another daughter and you missed out on 17 years of her life," Kristi said through her tears to Michael. "You have known about Ashley since the beginning! You've been promising to take the DNA test. How could you do something so cruel?"

Ashley said her biological father Michael has never been there for her and even refused to acknowledge that she was his daughter, TMZ confirmed. The only time Michael made any attempt to be in her life was in her early childhood.

In addition to the four children Michael has with his ex-wife Dina, he is expecting another child with long-time girlfriend Kate Major. 

Lindsay's appearance on "GMA" came days after she canceled an in-depth interview with ABC's Barbara Walters.

"Liz & Dick" premieres on Lifetime November 25 at 9/8c.

Watch the video below of Lindsay Lohan on "Good Morning America" looking shocked when asked if she was aware of her half-sister