Former child star Dawn Lyn, who starred in the popular '60s sitcom "My Three Sons" is in a coma after undergoing brain surgery.

The sad news was revealed by Lyn's former costars Stanley Livingston and Tina Cole who appeared alongside Lyn in the popular TV show.

"DAWN LYN. Just found out my little TV Sis', DAWN LYN (Dodie), is in a COMA and fighting for her life," Livingston wrote on his Facebook page Saturday. "She had surgery recently to remove a brain tumor. Please pray for her to have a swift and full recovery. I took Dawn out to lunch a couple of months ago. We had a great time reminiscing about our MTS days. Dawn is one of the nicest human beings I have ever known. Thoughts and prayers also go out to her husband, John, at this time. This is devastating news!"

Cole also posted a message Saturday on her Facebook page that read, "My heartfelt prayers go out to my "My Three Sons" sweet "lil' sis", Dawn Lyn (Dodie) and her husband John. Dawn is fighting for her life after undergoing brain surgery. I'm in touch with John and I will keep you all updated. Please keep her in your prayers as well."

Lyn's brother Leif Garrett told TMZ that his sister wanted her surgery to be a secret.

"My sister, Dawn, never wanted anyone to know about the surgery. Since it has been leaked on social media, I would really appreciate everyone's understanding that it has already been a difficult time having lost both of our parents and a cousin recently," Garrett said.

He also appealed to the public and said, "Please just keep my sister in your thoughts and prayers and respect our family's privacy. Thank you."

"My Three Sons" was aired from 1960 to 1972 and ran for five seasons on ABC and later moved to CBS for another seven seasons.

The sitcom told the story of a widower (played by Fred MacMurray) who is raising three sons with the help of his father-in-law and the boys' great-uncle. Lyn appeared as the main character's stepdaughter who was later formally adopted into the family.

Don Grady in a scene from "My Three Sons"
Don Grady in a scene from "My Three Sons" Screenshot