Inside 'NCIS' Star Mark Harmon's Bitter Custody Battle: Drugs, Booze, And Ricky Nelson

Mark Harmon can't escape his bitter feud with sister Kristin Harmon. The siblings have been fighting over their brutal custody battle 30 years ago and haven't been able to forgive each other since. Why haven't they been able to move on?

An inside source told Radar Online that the feud erupted after Kristin's ex-husband, Ricky Nelson, died in a plane crash in 1985. Mark immediately filed for the custody of Nelson and Kristen's son, Sam, because he didn't think she was a fit mom. Harmon says Kristin was addicted to drugs at the time.

The vicious custody fight that ensued is the source of their ongoing feud.

"Mark and Kristin have tried to let bygones be bygones," the insider shared. "But there's just too much bad blood for either of them to completely forgive and forget."

Kristin's ex-husband was also involved with drugs. Nelson was smoking freebase cocaine onboard the plane when he caused a fire that led to the crash. The accident took his life and six others.

Mark Harmon and Pam Dawber [Image by Kevin Winter/Image Direct]

In 1987, Mark and his wife, Pam Dawber, filed for custody of Sam while Kristin was in rehab. The NCIS star sought full custody of the child and told the court that Kristin's addiction to prescription drugs made her an unfit parent. Dawber even claimed that Kristin went shopping "blasted" and 12-year-old Sam didn't want to go home because he was afraid of his own mom.

Kristin didn't let the accusations fly without hitting back. OK! Magazine reports that her attorney's countered by saying Dawber used cocaine on the set of Mork & Mindy, which ran from 1978 to 1982 and starred the late Robin Williams.

Dawber was about to take the stand to defend against the accusations when Mark Harmon dropped the case. While Kristin's attorneys labeled his actions as an "unconditional surrender," she believes he dropped it to avoid more drama. Kristin eventually made a name for herself as an artist in New Mexico while Sam currently works as an actor and musician in Sherman Oaks, California.

"I knew from that time on that our family would never be the same again, and it hasn't been," Kristin reflected.

According to Radar Online, the feud runs so deep that Mark refuses to visit his sister, despite her bad health. Kristin, now 71, is on the verge of death in a New Mexico hospital, and Mark hasn't called or visited her.

"Kristin has gone from one medical crisis to the next," a close friend of the family shared. "Almost two years ago, Kris took a bad fall, and had to have fluid drained from her skull to relieve pressure on her brain. Mark was aware of it, but chose not to visit her."

Kristin is currently in an intensive care unit at Santa Fe's CHRISTUS St. Vincent Regional Medical Center. She was battling pneumonia, which later developed into a staph infection. To make it even worse, Kristin has run out of money to pay for her growing medical bills.

CBS NCIS, NCIS cast, Mark Harmon
Mark Harmon on 'NCIS' [Image by CBS]

Kristin inherited some money from her mom, who passed away in 2012, but burned through the inheritance fairly quickly. Now almost destitute, things couldn't get any worse for the dying artist.

With their feud alive and well, Mark hasn't offered any monetary support for his ailing sister. Mark, who ranks as one of television's highest paid actors, certainly has enough money to help his sister out. Unfortunately, their feud is proving too high an obstacle for the actor to reach out.

Kristin and Mark have not commented recently on their nasty feud.

Tell us! Whose side are you on – Mark Harmon or his sister Kristin? Let us know in the comments below.

[Featured Image by Mark Davis/Getty Images]