Brad Pitt has one major regret in Jennifer Aniston marriage

More details are coming out about Brad Pitt and Jennifer Aniston's relationship in the days following the actor's unexpected appearance at his ex-wife's 50th birthday last weekend.

The pair, who were married for five years between the years 2000 and 2005, had a brief reunion at Aniston's party at Sunset Tower on Saturday, as a star-studded crowd that included Ellen DeGeneres, George Clooney and Courteney Cox looked on "surprised" to see him in attendance.

"Brad gave Jen a card and a hug," an onlooker told Us Weekly about the interaction. "Brad seemed very hesitant [at first] -- all eyes were on him. [...] He came to support her, spoke to other friends of his that were there and headed out."

23 PHOTOS
Jennifer Aniston and Brad Pitt together
See Gallery
Jennifer Aniston and Brad Pitt together
LOS ANGELES - SEPTEMBER 12: Actor Brad Pitt and actress Jennifer Aniston attend the 51st Annual Primetime Emmy Awards on September 12, 1999 at Shrine Auditorium in Los Angeles, California. (Photo by Ron Galella, Ltd./WireImage)
Brad Pitt and Jennifer Aniston (Photo by Barry King/WireImage)
Jennifer Aniston and Brad Pitt shopping in Los Angeles, CA. November 23, 1999
UNITED STATES - circa 2000: Actress Jennifer Aniston with actor Brad Pitt. (Photo by The LIFE Picture Collection/Getty Images)
Jennifer Aniston and Brad Pitt (Photo by Jim Smeal/WireImage)
371747 01: Brad Pitt & Jennifer Aniston attending the Los Angeles Premiere of the new movie 'Erin Brockovich'. Westwood, California. March 14,2000. (Photo by: Brenda Chase Online USA Inc./Liaison Agency)
LOS ANGELES, CA - SEPTEMBER 10: Actor Brad Pitt and wife actress Jennifer Aniston arrive at the 52nd 2000 Primetime Emmy Awards on September 10, 2000 at the Shrine Auditorium in Los Angeles, California. (Photo by Ron Davis/Getty Images)
Brad Pitt and Jennifer Aniston at the premiere of 'The Mexican' at the National Theater in Los Angeles, Ca. 2/23/01. (Photo by Kevin Winter/Getty Images).
Brad Pitt and Jennifer Aniston during 'Rock Star' Los Angeles Premiere at Mann Village in Westwood, California, United States. (Photo by SGranitz/WireImage)
Jennifer Aniston & Brad Pitt during Spy Game Premiere at Mann National Theatre in Westwood, California, United States. (Photo by SGranitz/WireImage)
Jennifer Aniston and Brad Pitt arrive for the Golden Globe Awards at the Beverly Hilton Hotel in Beverly Hills, California January 20, 2002. (Photo by KMazur/WireImage)
Brad Pitt and Jennifer Aniston at the premiere of 'The Bourne Identity' at Universal CityWalk in Los Angeles, Ca. Thursday, June 6, 2002. Photo by Kevin Winter/ImageDirect
Jennifer Aniston and Brad Pitt arriving at the 54th Annual Prime Time Emmys. (Photo by Frank Trapper/Corbis via Getty Images)
UNITED STATES - JANUARY 12: Jennifer Aniston and Brad Pitt attending the premiere of 'Along Came Polly' at Grauman's Chinese Theater in Hollywood, CA 01/12/03 (Photo by Vinnie Zuffante/Getty Images)
SANTA MONICA, CA - MARCH 22: Actors Jennifer Aniston and husband Brad Pitt attend the 2003 IFP Independent Spirit Awards on March 22, 2003 in Santa Monica, California. (Photo by Jon Kopaloff/Getty Images)
Courteney Cox, Jennifer Aniston & Brad Pitt (Photo by Steve Granitz Archive 1/WireImage)
Brad Pitt and Jennifer Aniston at the Zeigfeld Theater in New York City, New York (Photo by Kevin Mazur/WireImage)
Brad Pitt, Jennifer Aniston during Warner Bros. Premiere of 'Troy' in New York City at Ziegfeld Theater in New York, New York, United States. (Photo by Sylvain Gaboury/FilmMagic)
CANNES, FRANCE - MAY 13: Actors Brad Pitt and Jennifer Aniston attend the World Premiere of epic movie 'Troy' at Le Palais de Festival on May 13, 2004 in Cannes, France. Aniston wears a dress by Versace. (Photo by Dave Hogan/Getty Images)
CANNES, France: US actor Brad Pitt and his wife Jennifer Aniston arrive for the official projection of US director Wolfgang Petersen's film 'Troy' , 13 May 2004, at the 57th Cannes Film Festival in the French Riviera town. Hollywood took over the French Riviera today as Brad Pitt and his co-stars of the epic movie arrived to present their 175 million dollar (147 million euro)-plus swords-and-sandals feature, being shown out of competition, in the blaze of Cannes publicity. AFP PHOTO/FRANCOIS GUILLOT (Photo credit should read FRANCOIS GUILLOT/AFP/Getty Images)
Actors Brad Pitt and Jennifer Aniston attend the premiere of Petersen's movie 'Troy', at the 57th Cannes film festival. (Photo by Stephane Cardinale/Corbis via Getty Images)
Jennifer Aniston and Brad Pitt at the The Shrine Auditorium in Los Angeles, California (Photo by Gregg DeGuire/WireImage)
Brad Pitt and Jennifer Aniston during The 56th Annual Primetime Emmy Awards - Audience at The Shrine Auditorium in Los Angeles, California, United States. ***Exclusive*** (Photo by Jeff Kravitz/FilmMagic)
HIDE CAPTION
SHOW CAPTION
of
SEE ALL
BACK TO SLIDE

Though their reconnection took many by surprise, those closest to the former couple insist that they've been in contact intermittently for the past few years ever since Pitt reached out to Aniston following her mother's death in May 2016.

"Brad contacted Jen after her mom died, and she was touched that he knew what a difficult time it was," a source explained. "They have each other’s cell phone number and communicate from time to time. This is nothing new. Jen and [Brad] have remained friendly."

Part of what also might've compelled Pitt to reach out to his famous ex? The regret he has around how their marriage dissolved amid claims that he cheated on her with Angelina Jolie while filming "Mr. and Mrs. Smith."

Though he "doesn't like to dwell on the past," a source told Us Weekly, he "of course wishes he'd handled the end of their marriage in a more thoughtful manner."

The insider added that Aniston has long forgiven her former husband for any transgressions that he may have made 15 years ago.

"He asked for Jen's forgiveness a long time ago," the source said. "And she gave it."

Both Brad Pitt and Jennifer Aniston are currently single. Aniston and Justin Theroux broke up in February 2018, while Pitt separated from soon-to-be ex-wife, Angelina Jolie, in September of 2016.

24 PHOTOS
The end of an era : Angelina Jolie and Brad Pitt
See Gallery
The end of an era : Angelina Jolie and Brad Pitt
U.S. actors Brad Pitt (L) and Angelina Jolie (R), stars of the new action film "Mr. & Mrs. Smith" pose with one of the film's producers, Arnon Milchan of New Regency at the film's premiere in Los Angeles June 7, 2005. The film opens in the United States on Friday. REUTERS/Fred Prouser fsp/TC
Hollywood star Brad Pitt carries adopted son Maddox as Angelina Jolie carries adopted daughter Zahara during their stroll outside their hotel in Mumbai November 12, 2006. REUTERS/Prashanth Vishwanathan (INDIA)
Actors Angelina Jolie and Brad Pitt kiss at their table during the 14th annual Screen Actors Guild Awards in Los Angeles January 27, 2008. REUTERS/Mario Anzuoni (UNITED STATES)
Cast member Angelina Jolie and actor Brad Pitt arrive for the screening of the film "The Exchange" by U.S. director Clint Eastwood at the 61st Cannes Film Festival May 20, 2008. REUTERS/Vincent Kessler (FRANCE)
U.S. actors Brad Pitt and Angelina Jolie arrive with their children at Narita airport, near Tokyo, January 27, 2009. Pitt is in Japan to promote the film "The Curious Case of Benjamin Button". From L-R: Pax, Knox Leon (carried by Pitt), Maddox (obscured), Zahara, Vivienne Marcheline (carried by Jolie) and Shiloh. REUTERS/Toru Hanai (JAPAN) FOR BEST QUALITY IMAGE SEE: GM1E5BB1OIM01
Cast member Angelina Jolie and actor Brad Pitt attend the premiere of the movie "Salt" at the Grauman's Chinese theatre in Hollywood, California July 19, 2010. The movie opens in the U.S. on July 23. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT)
Actors Brad Pitt (R) and Angelina Jolie are seen on the set of Jolie's yet untitled directorial debut in Budapest November 8, 2010. Jolie is directing her first feature film about a Serbian man and Bosnian woman who meet on the eve of the 1992-95 Bosnian war. REUTERS/Laszlo Balogh (HUNGARY - Tags: ENTERTAINMENT)
Cast member Brad Pitt and actress Angelina Jolie arrive on the red carpet for the screening of the film "The Tree of Life", by director Terrence Malick, in competition at the 64th Cannes Film Festival, May 16, 2011. REUTERS/Vincent Kessler (FRANCE - Tags: ENTERTAINMENT)
U.S. actor Brad Pitt (L) and his partner Angelina Jolie arrive at the Japan premiere of Pitt's film "Moneyball" in Tokyo November 9, 2011. REUTERS/Toru Hanai (JAPAN - Tags: ENTERTAINMENT TPX IMAGES OF THE DAY)
Actors Brad Pitt and Angelina Jolie depart at the end of the 18th annual Screen Actors Guild Awards in Los Angeles, California January 29, 2012. REUTERS/Lucy Nicholson (UNITED STATES - Tags: ENTERTAINMENT) (SAGAWARDS-SHOW)
Actors Brad Pitt and Angelina Jolie arrive at the 84th Academy Awards in Hollywood, California February 26, 2012. REUTERS/Lucy Nicholson (UNITED STATES - Tags: ENTERTAINMENT) (OSCARS-ARRIVALS)
Angelina Jolie and Brad Pitt attend the "Cinema for Peace 2012" charity gala during the 62nd Berlinale film festival in Berlin February 13, 2012. REUTERS/Andreas Rentz/Pool (GERMANY - Tags: ENTERTAINMENT) SOCIETY)
An aerial view of the 17th-century Chateau Miraval, the $60 million estate which is owned by actors Brad Pitt and Angelina Jolie, is seen in the village of Correns, southern France, August 10, 2012. Rumours of a weekend wedding between Brad Pitt and Angelina Jolie have been denied by a local newspaper and local officials said they had no knowledge of any impending nuptials. Since Pitt and Jolie announced their engagement earlier this year, there have been rumours that they could tied the knot this summer at their estate. REUTERS/Philippe Laurenson (FRANCE - Tags: ENTERTAINMENT)
Actress and Special Envoy of the United Nations High Commissioner for Refugees, Angelina Jolie (R), and her partner actor Brad Pitt, look at photographs of victims of violence at the 'End Sexual Violence in Conflict' summit in London June 12, 2014. REUTERS/Lefteris Pitarakis/Pool (BRITAIN - Tags: SOCIETY CRIME LAW CIVIL UNREST)
Cast member Brad Pitt and his fiance Angelina Jolie arrive for the premiere of the film World War Z in Berlin June 4, 2013. The movie opens in German cinemas on June 27. REUTERS/Tobias Schwarz (GERMANY - Tags: ENTERTAINMENT)
Hollywood actors Brad Pitt (R) and actress Angelina Jolie (2nd L) arrive with their children Knox (2nd R), Vivienne (3rd L) and Pax (L) at Haneda international airport in Tokyo July 28, 2013. Pitt flew into Japan on Sunday with Jolie and his children to attend promotional events of his movie "World War Z". REUTERS/Issei Kato (JAPAN - Tags: ENTERTAINMENT)
Hollywood actor Brad Pitt and his partner Angelina Jolie pose at the Japan premiere of his movie "World War Z" in Tokyo July 29, 2013. The movie will be screened in Japan on August 10, 2013. REUTERS/Yuya Shino 
Angelina Jolie and partner Brad Pitt and son Maddox arrive at the 5th Annual Academy of Motion Picture Arts and Sciences Governors Awards in Hollywood November 16, 2013. Jolie is being honored with the Jean Hersholt Humanitarian Award, which is an Oscar statuette at the ceremony. REUTERS/Fred Prouser (UNITED STATES - Tags: ENTERTAINMENT)
Actress Angelina Jolie kisses her partner, actor Brad Pitt, as she is announced recipient of the Jean Hersholt Humanitarian Award at the 5th Annual Academy of Motion Picture Arts and Sciences Governors Awards at The Ray Dolby Ballroom in Hollywood, California November 16, 2013. REUTERS/Mario Anzuoni (UNITED STATES - Tags: ENTERTAINMENT TPX IMAGES OF THE DAY)
Actors Brad Pitt and Angelina Jolie arrive at the British Academy of Film and Arts (BAFTA) awards ceremony at the Royal Opera House in London February 16, 2014. REUTERS/Suzanne Plunkett 
Actors Brad Pitt and Angelina Jolie arrive for a special Maleficent Costume Display at Kensington Palace in London May 8, 2014. "Maleficent" is the upcoming Disney film starring Jolie and Kensington Palace is the official residence of Prince William and Catherine, Duchess of Cambridge. REUTERS/Luke MacGregor (BRITAIN - Tags: ENTERTAINMENT FASHION SOCIETY ROYALS)
Cast member Angelina Jolie waves at fans with actor Brad Pitt as they arrive at the premiere of "Maleficent" at El Capitan theatre in Hollywood, California May 28, 2014. The movie opens in the U.S. on May 30. REUTERS/Mario Anzuoni 
Angelina Jolie (L) and Brad Pitt arrive at the British Academy of Film and Arts (BAFTA) awards ceremony at the Royal Opera House in London February 16, 2014. REUTERS/Suzanne Plunkett (BRITAIN - Tags: ENTERTAINMENT)
Director and cast member Angelina Jolie and her husband and co-star Brad Pitt pose at the premiere of "By the Sea" during the opening night of AFI FEST 2015 in Hollywood, California November 5, 2015. The movie opens in the U.S. on November 13. REUTERS/Mario Anzuoni
HIDE CAPTION
SHOW CAPTION
of
SEE ALL
BACK TO SLIDE

Read Full Story

Sign up for Entertainment Insider by AOL to get the hottest pop culture news delivered straight to your inbox!

Subscribe to our other newsletters

Emails may offer personalized content or ads. Learn more. You may unsubscribe any time.