"My brother, Carter Cooper. Jan 27, 1965 - July 22, 1988. Hard to believe it has been 29 years. He remains in my heart, golden and true," Anderson wrote on Instagram alongside a black-and-white photo of the two as children.
Cooper's mother, Gloria Vanderbilt, also took to Instagram to remember her son. "Not a day goes by that I do not think of him. He is close to me because he lives in my mind and heart forever," she captioned the slideshow.
WATCH WHAT HAPPENS LIVE -- Pictured: Anderson Cooper -- (Photo by: Charles Sykes/Bravo/NBCU Photo Bank via Getty Images)
NEW YORK, NY - NOVEMBER 18: (L-R) Jeffrey Zucker and Anderson Cooper attend the 2014 CNN Heroes: An All-Star Tribute at the American Museum of Natural History on November 18, 2014 in New York City. (Photo by Andrew H. Walker/Getty Images)
WATCH WHAT HAPPENS LIVE -- Pictured (l-r): Kelly Ripa and Anderson Cooper -- (Photo by: Charles Sykes/Bravo/NBCU Photo Bank via Getty Images)
LATE NIGHT WITH SETH MEYERS -- Episode 0016 -- Pictured: (l-r) Journalist Anderson Cooper during an interview with host Seth Meyers on March 17, 2014 -- (Photo by: Peter Kramer/NBC/NBCU Photo Bank via Getty Images)
BEVERLY HILLS, CA - JANUARY 11: Sean Penn and Anderson Cooper attend the 3rd annual Sean Penn & Friends HELP HAITI HOME Gala benefiting J/P HRO presented by Giorgio Armani at Montage Beverly Hills on January 11, 2014 in Beverly Hills, California. (Photo by Kevin Mazur/Getty Images for J/P Haitian Relief Organization)
NEW YORK, NY - NOVEMBER 08: (EXCLUSIVE COVERAGE) (L-R) Anderson Cooper, Kathy Griffin and Gloria Steinem attend Kathy Griffin's Carnegie Hall Performance official after party hosted by Anderson Cooper at Trattoria Dell Arte Restaurant on November 8, 2013 in New York City. (Photo by Rob Kim/Getty Images)
NEW YORK, NY - AUGUST 27: Television personality Anderson Cooper arrives to 'Late Show with David Letterman' at Ed Sullivan Theater on August 27, 2013 in New York City. (Photo by Jeffrey Ufberg/WireImage)
WATCH WHAT HAPPENS LIVE -- Pictured (l-r): Anderson Cooper and Cher -- Photo by: Charles Sykes/Bravo/NBCU Photo Bank via Getty Images
NEW YORK, NY - MARCH 16: Anderson Cooper attends the 24th annual GLAAD Media awards at The New York Marriott Marquis on March 16, 2013 in New York City. (Photo by Michael Stewart/WireImage)
NEW YORK, NY - JANUARY 08: (L-R) Actress Betty White, television personality Lisa Vanderpump, and media personality Anderson Cooper pose for a picture as 'RHOBH' Lisa Vanderpump Co-Host's Anderson Live With Guest Betty White at CBS Studios on January 8, 2013 in New York City. (Photo by Mike Coppola/Getty Images for Anderson Live)
NEW YORK, NY - DECEMBER 04: (EXCLUSIVE COVERAGE) Anderson Cooper and Christie Brinkley host Anderson Live at CBS Studios on December 4, 2012 in New York City. (Photo by Neilson Barnard/Getty Images for Anderson Live)
Honoree Pushpa Basnet the Early Childhood Development Center and host Anderson Cooper onstage during the CNN Heroes: An All Star Tribute
at The Shrine Auditorium on December 2, 2012 in Los Angeles, California. 23046_006_MB_2354.JPG
WASHINGTON, DC - JULY 21: Bill Gates, and Anderson Cooper attend Together To End AIDS: An Evening To Benefit amfAR and GBCHealth at John F. Kennedy Center for the Performing Arts on July 21, 2012 in Washington, DC. (Photo by Kevin Mazur/WireImage)
WEST HOLLYWOOD, CA - FEBRUARY 26: TV personality Anderson Cooper arrives at the 2012 Vanity Fair Oscar Party hosted by Graydon Carter at Sunset Tower on February 26, 2012 in West Hollywood, California. (Photo by Alberto E. Rodriguez/Getty Images)
NEW YORK, NY - OCTOBER 12: Anderson Cooper tapes a segment for his talk show 'Anderson' at Boston Market on October 12, 2011 in New York City. (Photo by Neilson Barnard/Getty Images for Anderson)
NEW YORK CITY, NY - SEPTEMBER 27: Anderson Cooper seen in the Meatpacking District on September 27, 2011 in New York City, New York. (Photo by Josiah Kamau/BuzzFoto/FilmMagic)
NEW YORK, NY - SEPTEMBER 14: Journalist Anderson Cooper unveils his wax figure at Madame Tussauds on September 14, 2011 in New York City. (Photo by Charles Eshelman/WireImage)
NEW YORK, NY - AUGUST 19: (EXCLUSIVE COVERAGE) Anderson Cooper visits Elvis Duran and Z100 morning show team at the Z100 Studios on August 19, 2011 in New York City. (Photo by Neilson Barnard/Getty Images for the Z100 Morning Show)
INDIANAPOLIS, IN - MAY 28: Anderson Cooper, honorary marshall for the 95th running of Indianapolis 500 during the parade for the 100th Anniversary of the Indianapolis 500 on May 28, 2011 in the streets of Indianapolis, Indiana. (Photo by Robert Laberge/Getty Images)
Anderson Cooper sighting at Time Warner building on May 9, 2011 in New York City.
NEW YORK, NY - NOVEMBER 15: Anderson Cooper attends Hope for Depression Research Foundation 10th Annual Hope Luncheon Seminar at The Plaza Hotel on November 15, 2016 in New York City. (Photo by Jared Siskin/Patrick McMullan via Getty Images)
***USA OUT***CANADA OK***
NEW YORK - MAY 18: Anderson Cooper seen at the 2016 Turner Upfront held at Nick & Stef's Steakhouse on May 18, 2016 in New York City.
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TORONTO, ON - MAY 15: CEO of Indigo Heather Reisman and Anderson Cooper attend the book signing of his new book 'The Rainbow Comes And Goes' at Indigo Manulife Centre on May 15, 2016 in Toronto, Canada. (Photo by GP Images/WireImage)
NEW YORK, NY - APRIL 15: Anderson Cooper attends AOL Build Speaker Series to discuss 'Nothing Left Unsaid' at AOL Studios In New York on April 15, 2016 in New York City. (Photo by Laura Cavanaugh/Getty Images)
NEW YORK, NEW YORK - APRIL 04: Anderson Cooper and Gloria Vanderbilt attend the 'Nothing Left Unsaid' premiere at Time Warner Center on April 4, 2016 in New York City. (Photo by Donna Ward/Getty Images)
NEW YORK, NEW YORK - APRIL 04: Anderson Cooper visits at SiriusXM Studio on April 4, 2016 in New York City. (Photo by Robin Marchant/Getty Images)
NEW YORK, NEW YORK - APRIL 07: Gloria Vanderbilt and Anderson Cooper in conversation at Barnes & Noble Union Square on April 7, 2016 in New York City. (Photo by John Lamparski/Getty Images)
MILWAUKEE, WI - MARCH 29: Republican Presidential candidate Ohio Gov. John Kasich takes part in a town hall event moderated by Anderson Cooper March 29, 2016 in Milwaukee, Wisconsin. Candidates are campaigning in Wisconsin ahead of the state's April 5th primary. (Photo by Darren Hauck/Getty Images)
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Carter's death came 10 years after his father, Wyatt Cooper, died during heart bypass surgery. The then-23-year-old committed suicide by jumping from the terrace of his family's Manhattan penthouse.
Vanderbilt and Anderson's life story was recently told in the memoir The Rainbow Comes and Goes: A Mother and Son Talk About Life, Love, and Loss, and in the 2016 documentary, Nothing Left Unsaid: Gloria Vanderbilt and Anderson Cooper, which debuted at Sundance and premiered on HBO in April of that year.