Katie Cassidy on father David Cassidy: What the world 'doesn't know'

Katie Cassidy is ready to speak more openly about her father, the late David Cassidy.

It's long been known that the "Arrow" star had a complicated relationship with David, although few details were known about just how messy it was.

"I didn't meet my father until I was in the fourth grade," Katie told Us Weekly. "The world doesn’t know that. Not because I’m hiding it, it just hasn’t been discussed."

Now 31 years old, Katie said that at a time, she and David had a great relationship, but that may not have been the case in recent years.

“My biological father and I had a really good relationship at one point," she said. "He was one of my close friends and gave me wonderful advice."

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David Cassidy and Katie Cassidy together
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David Cassidy and Katie Cassidy together
LOS ANGELES, CA - NOVEMBER 28: Katie Cassidy and David Cassidy arrive at the 9th annual Family Television Awards held at the Beverly Hilton Hotel on November 28, 2007 in Los Angeles, California. (Photo by Jean Baptiste Lacroix/WireImage)
LOS ANGELES, CA - NOVEMBER 28: Katie Cassidy and David Cassidy arrive at the 9th annual Family Television Awards held at the Beverly Hilton Hotel on November 28, 2007 in Los Angeles, California. (Photo by Jean Baptiste Lacroix/WireImage)
LOS ANGELES, CA - NOVEMBER 28: Katie Cassidy and David Cassidy arrive at the 9th annual Family Television Awards held at the Beverly Hilton Hotel on November 28, 2007 in Los Angeles, California. (Photo by Jean Baptiste Lacroix/WireImage)
LOS ANGELES, CA - NOVEMBER 28: Katie Cassidy and David Cassidy arrive at the 9th annual Family Television Awards held at the Beverly Hilton Hotel on November 28, 2007 in Los Angeles, California. (Photo by Jean Baptiste Lacroix/WireImage)
LOS ANGELES, CA - NOVEMBER 28: Singer/actor David Cassidy (R) and his daughter Katie Cassidy arrive at the 9th annual Family Television Awards held at the Beverly Hilton Hotel on November 28, 2007 in Los Angeles, California. (Photo by Michael Buckner/Getty Images for Family TV Awards)
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But although David was a "wonderful, wonderful person," Katie said, "sadly, he had some demons. There is a silver lining in all of that. You live and learn and it has brought my family closer together so I’m grateful for that."

David Cassidy died at 67, not long after publicly sharing his dementia diagnosis. He had a long history of substance abuse dating nearly as far back as his "Partridge Family" days.

After his death, headlines swirled that the actor/singer had left Katie out of his will.

Katie, for her part, is moving forward with positive updates in her life: She's engaged to marry later this year.

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David Cassidy through the years
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David Cassidy through the years
UNITED STATES - JULY 28: THE PARTRIDGE FAMILY - 'Gallery' 1971 David Cassidy (Photo by ABC Photo Archives/ABC via Getty Images)
TODAY -- Pictured: (l-r) NBC News' Savannah Guthrie, Natalie Morales and musician/actor David Cassidy appear on NBC News' 'Today' show on March 21, 2013 -- (Photo by: Peter Kramer/NBC/NBC NewsWire via Getty Images)
HOLLYWOOD, CA - DECEMBER 14: Singer David Cassidy performs at Hollywood Today Live at W Hollywood on December 14, 2016 in Hollywood, California. (Photo by David Livingston/Getty Images)
UNITED STATES - JULY 28: THE PARTRIDGE FAMILY - 'Gallery' 1971 David Cassidy (Photo by ABC Photo Archives/ABC via Getty Images)
NEW YORK, NY - JANUARY 10: Musician David Cassidy performs at BB King on January 10, 2015 in New York City. (Photo by Debra L Rothenberg/Getty Images)
UNITED STATES - JULY 28: THE PARTRIDGE FAMILY - 'Gallery' 1971 David Cassidy (Photo by ABC Photo Archives/ABC via Getty Images)
TODAY -- Pictured: (l-r) David Cassidy and Danny Bonaduce appear on NBC News' 'Today' show (Photo by Peter Kramer/NBC/NBCU Photo Bank via Getty Images)
HOLLYWOOD, FL - DECEMBER 12: David Cassidy attends Seminole Hard Rock Winterfest Boat Parade 2014 Grand Marshal Reception Honors Flo Rida at Seminole Hard Rock Hotel & Casino ? Hard Rock Cafe Hollywood on December 12, 2014 in Hollywood, Florida. (Photo by Larry Marano/Getty Images)
David Cassidy, singer, actor and musician, in concert at Wembley Arena, London. David Bruce Cassidy is widely known for his role as Keith Partridge in the 1970s musical sitcom The Partridge Family, which led to his becoming one of pop culture's most celebrated teen idols and pop singers of the 1970s. He later had a career in both acting and music. Picture taken 17th March 1973. (Photo by Lloyd/Mirrorpix/Getty Images)
HOLLYWOOD, FL - DECEMBER 12: Sue Shifrin and David Cassidy attend Seminole Hard Rock Winterfest Boat Parade 2014 Grand Marshal Reception Honors Flo Rida at Seminole Hard Rock Hotel & Casino ? Hard Rock Cafe Hollywood on December 12, 2014 in Hollywood, Florida. (Photo by Larry Marano/Getty Images)
UNITED STATES - JULY 28: THE PARTRIDGE FAMILY - 'The Last Howard' 10/27/73 David Cassidy (Photo by ABC Photo Archives/ABC via Getty Images)
TODAY -- Pictured: Musician/actor David Cassidy appears on NBC News' 'Today' show on March 21, 2013 -- (Photo by: Peter Kramer/NBC/NBC NewsWire via Getty Images)
UNITED STATES - JULY 22: THE PARTRIDGE FAMILY - 'The Forty-Year Itch' 11/1971 David Cassidy (Photo by ABC Photo Archives/ABC via Getty Images)
SCHODACK, NY - AUGUST 21: In this handout photo provided by the Schodack Police Department, David Cassidy is seen in a police booking photo after his arrest on charges of felony DWI, driving while intoxicated, August 21, 2013 in Schodack, New York. Cassidy was released on USD 2,500 bail and is scheduled to appear in court September 4. (Photo by Schodack Police Department via WireImage)
COCONUT CREEK, FL - AUGUST 13: Singer David Cassidy performs during the first hand of Real Blackjack 24/7 Seminole Casino Coconut Creek on August 13, 2010 in Coconut Creek, Florida. (Photo by Larry Marano/Getty Images)
TODAY -- Pictured: Musician/actor David Cassidy appears on NBC News' 'Today' show on March 21, 2013 -- (Photo by: Peter Kramer/NBC/NBC NewsWire via Getty Images)
TODAY -- Pictured: (l-r) NBC News' Matt Lauer, David Cassidy, tv host George Oliphant and NBC News' Natalie Morales appear on NBC News' 'Today' show on March 21, 2013 -- (Photo by: Peter Kramer/NBC/NBC NewsWire via Getty Images)
BIRMINGHAM, UNITED KINGDOM - NOVEMBER 09: David Cassidy performs on stage during the UK Once In A Lifetime Tour at LG Arena on November 9, 2012 in Birmingham, United Kingdom. (Photo by Steve Thorne/Redferns via Getty Images)
UNITED STATES - JULY 28: THE PARTRIDGE FAMILY - 'Gallery' 1970 Susan Dey, Jeremy Gelbwaks, David Cassidy, Shirley Jones, Danny Bonaduce, Suzanne Crough (Photo by ABC Photo Archives/ABC via Getty Images)
NEW YORK, NY - JULY 19: Singer David Cassidy performs at BB King on July 19, 2012 in New York City. (Photo by Bobby Bank/Getty Images)
NEW YORK - NOVEMBER 21: David Cassidy performs at the Queensborough Performing Arts Center in Queens on November 21, 2009 in New York City. (Photo by Bobby Bank/WireImage)
NEW YORK, NY - MAY 22: David Cassidy attends 'The Celebrity Apprentice' Season 4 Finale at Trump SoHo on May 22, 2011 in New York City. (Photo by Jim Spellman/WireImage)
LONDON, UNITED KINGDOM - APRIL 12: David Cassidy performs on stage at Hammersmith Apollo on April 12, 2011 in London, United Kingdom. (Photo by Mark Westwood/Redferns)
UNITED STATES - JULY 28: THE PARTRIDGE FAMILY - 'Gallery' 1971 Shirley Jones, David Cassidy (Photo by ABC Photo Archives/ABC via Getty Images)
TODAY -- Pictured: David Cassidy appears on NBC News' 'Today' show (Photo by Peter Kramer/NBC/NBCU Photo Bank via Getty Images)
David Cassidy enter caption here at The Langham Resort on August 8, 2009 in Pasadena, California. (Photo by Steve Granitz/WireImage)
NEW YORK, NY - JULY 19: Singer David Cassidy performs at BB King on July 19, 2012 in New York City. (Photo by Bobby Bank/Getty Images)
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