In a recent interview with Esquire, the 37-year-old racecar driver reveals he has know about Caitlyn's "secret" for the past 25 years.
"A lot of people don't know that this is something that I've known now for, I think, 25 years."
Burt Jenner, Esquire
Although the oldest Jenner doesn't necessarily want to be part of the reality show circuit, he wants people to know he has always been a supporter of his father.
"Before I was allowed to tell anybody, or before my dad even knew that I knew, I went and marched on behalf of Prop 8 through the streets of Los Angeles," Jenner told Esquire.
"I've always tried to be an outspoken supporter of the LGBT community."
Burt Jenner, Esquire
See the evolution of the Kardashian/Jenner clan:
The evolution of the Kardashian/Jenner clan
Caitlyn Jenner's oldest son reveals how long he's known of father's secret
With his son Burt on his shoulders, American former professional athlete Bruce Jenner walks around the dirt race course during a break in the First Off-Road Championship Grand Prix in the Los Angeles Memorial Coliseum, Los Angeles, California, June 24, 1979. (Photo by Bob Riha, Jr./Getty Images)
LOS ANGELES - 1991: (Middle row, L-R) Brody Jenner, Kourtney Kardashian, Bruce Jenner, Kris Jenner, Cassandra Jenner, Kim Kardashian, (top row, L-R) Brandon Jenner, Burton Jenner,(bottom row, L-R) Robert Kardashian, Jr., Khloe Kardashian of the celebrity Jenner and Kardashian families featured in the TV show 'Keeping Up With The Kardashians' pose for a family portrait in 1991 in Los Angeles, California . (Photo by Maureen Donaldson/Michael Ochs Archives/Getty Images)
LOS ANGELES - 1993: (clockwise from top left) Burton Jenner, Khloe Kardashian, Bruce Jenner, Kris Jenner, Kim Kardashian, Brandon Jenner, Brody Jenner, Kourtney Kardashian, Robert Kardashian, Jr. and Cassandra Jenner of the celebrity Jenner and Kardashian families featured in the TV show 'Keeping Up With The Kardashians' pose for a family portrait in 1993 in Los Angeles, California . (Photo by Maureen Donaldson/Michael Ochs Archives/Getty Images)
Bruce Jenner, Kendall Jenner and Kris Kardashian during World Premiere of 'Mulan' at Hollywood Bowl in Hollywood, California, United States. (Photo by Ron Galella, Ltd./WireImage)
HOLLYWOOD, CA - DECEMBER 10: Bruce Jenner, Kris Jenner, Kendall Jenner and Kylie Jenner attend the world premiere of 'The Emperor's New Groove' on December 10, 2000 at the El Capitan Theater in Hollywood, California. (Photo by Ron Galella, Ltd./WireImage)
Bruce Jenner and wife Kris with daughters Kylie and Kendall (Photo by Cesare Bonazza/WireImage)
LOS ANGELES - JULY 29: Musician Brandon Jenner performs with his band Big Dume at Best Buy West Los Angeles on July 29, 2005 in Los Angeles, California. (Photo by Amanda Edwards/Getty Images)
LOS ANGELES, CA - OCTOBER 10: Kris Jenner, Kourtney Kardashian, Kim Kardashian and Khloe Kardashian attend Nick Cannon's Birthday celebration and opening of the PNB Nation store on October 10, 2006 in Los Angeles, California. (Photo by Chad Buchanan/Getty Images)
Kylie Jenner, Kim Kardashian and Kendall Jenner (Photo by Jeff Vespa/WireImage)
Brody Jenner arrives at the MTV Movie Awards on Sunday June 1, 2008 in Los Angeles. (AP Photo/Chris Pizzello)
LOS ANGELES, CA - SEPTEMBER 25: Scott Disick (L) and TV personality Kourtney Kardashian attend 'Rock The Vote' Hosted by Christina Aguilera held at the Esquire House Hollywood Hills on September 25, 2008 in Los Angeles, California. (Photo by Frazer Harrison/Getty Images for Esquire )
From left, television personalities Kim, Kourtney and Khloe Kardashian participate in the 2nd Annual DirecTV Celebrity Beach Bowl presented by Spike, Thursday, Jan. 31, 2008 in Scottsdale, Ariz. (AP Photo/Evan Agostini)
Brody Jenner arrives to the 6th Annual Hollywood Style Awards on Sunday Oct. 11, 2009, in Los Angeles. (AP Photo/Katy Winn)
Reality stars Kim Kardashian, Kourtney Kardashian and Scott Disick attend the Jill Stuart Spring 2011 collection during fashion week at Lincoln Center, in New York, on Saturday, Sept. 11, 2010. (AP Photo/Peter Kramer)
EXCLUSIVE CONTENT - PREMIUM RATES APPLY Burt Jenner, Bruce Jenner, Brody Jenner and Brandon Jenner at Brody Jennerâs 30th Birthday Celebration with Stoli held at Aventine on August 21, 2013 in Los Angeles. (Photo by Alexandra Wyman/Invision for Stoli/AP Images)
LAS VEGAS, NV - SEPTEMBER 21: (L-R) TV personalities Kendall Jenner, Khloe Kardashian, Kourtney Kardashian and Kylie Jenner attend the iHeartRadio Music Festival at the MGM Grand Garden Arena on September 21, 2013 in Las Vegas, Nevada. (Photo by David Becker/Getty Images for Clear Channel)
LOS ANGELES, CA - APRIL 05: Musicians Brandon Jenner (L) and Leah Felder attend the 2nd Light Up The Blues Concert - An Evening Of Music To Benefit Autism Speaks at The Theatre At Ace Hotel on April 5, 2014 in Los Angeles, California. (Photo by Imeh Akpanudosen/Getty Images for LUTB)
Burt Jenner speaks during a news conference after winning the SPEED Energy Formula Off-Road race before the IndyCar Detroit Grand Prix auto racing doubleheader Sunday, May 31, 2015. (Photo/Paul Sancya)
LOS ANGELES, CA - APRIL 23: TV personalities Scott Disick (L) and Kourtney Kardashian attend Opening Ceremony and Calvin Klein Jeans' celebration launch of the #mycalvins Denim Series with special guest Kendall Jenner at Chateau Marmont on April 23, 2015 in Los Angeles, California. (Photo by Chris Weeks/Getty Images for Calvin Klein)
Brody Jenner arrives at the LA Premiere Of "Entourage" at the Regency Village Theatre on Monday, June 1, 2015, in Los Angeles. (Photo by Rob Latour/Invision/AP)
FILE - In this June 24, 2015 file photo, American television personality Kim Kardashian poses for photographers as she attends the Cannes Lions 2015 in Cannes, southern France. The reality TV star is scheduled to speak and sign copies of her new coffee table book âSelfishâ during a Tuesday, June 30 night event hosted by the Commonwealth Club of California, which bills itself as the nation's oldest and largest public affairs forum.(AP Photo/Lionel Cironneau, File)
Kylie Jenner, sister of Kim Kardashian poses during a photocall at the Cannes Lions 2015, International Advertising Festival in Cannes, southern France, Wednesday, June 24, 2015. The Cannes Lions International Advertising Festival is a world's meeting place for professionals in the communications industry.(AP Photo/Lionel Cironneau)
Khloe Kardashian attends the NBCUniversal Cable Entertainment 2015 Upfront at The Javits Center on Thursday, May 14, 2015, in New York. (Photo by Evan Agostini/Invision/AP)
LOS ANGELES, CA - APRIL 23: TV personalities Kris Jenner (L) and Kourtney Kardashian attend Opening Ceremony and Calvin Klein Jeans' celebration launch of the #mycalvins Denim Series with special guest Kendall Jenner at Chateau Marmont on April 23, 2015 in Los Angeles, California. (Photo by John Sciulli/Getty Images for Calvin Klein)
NEW YORK, NY - JUNE 17: Kendall Jenner attends the 2015 Fragrance Foundation Awards at Alice Tully Hall at Lincoln Center on June 17, 2015 in New York City. (Photo by Michael Loccisano/Getty Images for Fragrance Foundation)