AceShowbiz - Mark Harmon is mourning the death of his actress and painter sister Kristin Nelson. The older sister of "NCIS: Naval Criminal Investigative Service" star Mark Harmon and fellow actress/model Kelly Harmon passed away unexpectedly on 27 April after suffering a heart attack, her daughter Tracy Nelson announced in a post on Facebook. She was 72.

The daughter of sportsman Tom Harmon and actress Elyse Knox, Kristin rose to fame in the 1960s after teaming up with her husband, pop singer Ricky Nelson, to appear as his wife on his family radio and TV show "The Adventures of Ozzie and Harriet".

Kristin also co-starred with Ricky in 1965 romantic comedy "Love and Kisses", and featured in the Oscar-winning short film "The Resurrection of Broncho Billy", and Matt Dillon film "Liar's Moon" in 1982, after which she retired from the screen.

She later pursued painting as a career, and reportedly found fans in former U.S. First Lady Jacqueline Kennedy, actresses Mia Farrow and Tyne Daly, and country star Dwight Yoakam.

Her marriage to Ricky, the father of her four children, began to break down in the 1970s, amid claims of heavy drug and alcohol use, and they eventually divorced in 1982, three years before the singer was killed in a plane crash.

Meanwhile, her relationship with her brother Mark became strained after he and his wife, Pam Dawber, won temporary custody of Kristin's youngest son, Sam, in 1987, as she continued to battle substance abuse issues.

She eventually regained custody, and in 1988, wed her second husband, Mark Tinker. They divorced in 2000.

Kristin and Ricky were also parents to actress Tracy, and twin boys Gunnar and Matthew, who formed the rock band Nelson.