The loss of a child is said to be the worst pain a parent can experience. With all their fame and money, celebrities are not immune: John Travolta and Kelly Preston are busy preparing for the funeral for their 16-year-old son Jett, who died last week from a seizure.

It is unclear what exactly was wrong with Jett. The couple said he suffered from Kawasaki disease, which causes inflammation of the arteries.

The actors denied reports that the teen had autism, which is associated with seizures; Kawasaki is not, generally, say experts. Regardless, the couple said in a statement that they are "heartbroken that our time with him was so brief."

Herewith, other celebrities who have suffered tragic loss:

• Lark Previn, a daughter of actress Mia Farrow whose sister Soon-Yi Previn was at the center of Farrow's messy breakup with Woody Allen, died at 35 on Christmas Day. The Vietnam native - one of three children adopted by Farrow and her then-husband, conductor Andre Previn - had been suffering an illness but the cause of her death was not released. If you believe Star magazine, Lark got AIDS from a tattooist's needle in the early '90s.

The "Rosemary's Baby" star also dealt with the death of her daughter Tam, who died at 19 from heart failure in 2000.

• The coroner's report recently came in regarding the death of Andre Young Jr., the son of veteran rapper Dr. Dre (real name Andre Young). The 20-year-old died in August from an overdose of heroin and morphine. He was found dead at his Los Angeles home by his mother after spending a night out with friends.

• Last fall Hunter Tylo's 19-year old son, Michael Tylo Jr., drowned in the family pool near Las Vegas. It is believed he suffered a seizure and fell into the pool after stepping outside to use his cellphone.

• In 1979, O.J. Simpson's daughter Aaren also drowned in the family's swimming pool a month before her second birthday. That same year, Simpson and his first wife Marguerite divorced.

• Carroll O'Connor's son Hugh - who appeared in the TV version of "In the Heat of the Night" with his dad - shot himself in the head at the age of 32 in 1995. Adopted when he was 6 days old, Hugh was named after the late "All in the Family" star's brother, who was killed in a motorcycle accident. When Hugh was 16 he survived Hodgkins lymphoma, but later became addicted to prescription drugs and cocaine. He called his father right before ending his life.

• Ennis Cosby, the only son of Bill and Camille Cosby, was shot and killed by a 19-year-old Ukrainian immigrant Mikail Markhasev, in 1997 as the 27-year-old stopped to change a tire on the San Diego Freeway. Robbery was the motive; Markhasev is serving a life sentence.

• Eric Clapton won a Grammy for "Tears in Heaven," his tribute to his 4-year-old son Connor, who tumbled out of a window of a Manhattan high-rise in 1991. "I went into shock," the singer told "Access Hollywood" last year. "You know, it's incomprehensible. I think there is an area around my grief that's almost like - no personnel allowed in there, you know? I mean, it's just a shut door."

• Anna Nicole Smith's 20-year-old son Daniel died while visiting his mother at the maternity ward in a Bahamas hospital Sept. 10, 2006, after she had given birth to his half-sister, Dannielynn. The cause was an accidental overdose of Zoloft, methadone and Lexapro, according to pathologist Dr. Cyril Wecht, who also conducted Jett Travolta's autopsy.

Anna Nicole died five months later at her suite at the Seminole Hard Rock Hotel & Casino near Hollywood at the age of 39. Cause of death: accidental overdose.

• Xzibit's premature newborn son Xavier's lungs gave out last May. "It is unnatural for a parent to bury a child," the rapper (real name: Alvin Nathaniel Joiner) wrote on his blog soon after. "Hold on to your kids if you have them, protect them and show them you love them every day you wake up and see them, don't take a second you get to hug them, teach them and care for them for granted. You can have all the material wealth in the universe but it is nothing compared to having your family."