The two air their thoughts on the issue during tomorrow night's episode of Keeping Up with the Kardashians.
Kris Jenner confessed to the fling in her recent autobiography.
Bonding: Kim Kardashian and Kris Jenner were seen bonding on Friday in Los Angeles as they set off together for the gym
Kris and Robert divorced and in 1991, Kris married Bruce Jenner.
As they talked, Kourtney revealed that she was angry that her other included the infidelity in her book.
Heart to heart: Kim and Kourtney discussed their mother's affair over lunch on Keep Up with the Kardashians
Looking for answers: Kim suggested Kourtney discuss the the affair with their mother Kris
Emotional: Kim cried as she chatted with her sister
Speaking out: Kim will open up about her mother's affair on tomorrow night's episode of Keeping Up with the KardashiansKim told her to talk it through with their mother because 'you have this resentment towards mom.'
But despite the revelation of the affair, Kim and Kris are just as close as ever.
The two were spotted this weekend in Beverly Hills for a round of exercise.
Maintaining her curves: Kim set off for the gym immediately after returning from the Cannes Film Festival
Pamper time: Kim was seen going to the nail salon later in the day
She wore knee length black leggings, a black tank top, over a black and white fitness bra, and neon green Nike Trainers.
Kris wore long black leggings and a blue exercise jacket. The star hit the gym, within hours of arriving back in California from the Cannes Film Festival in France.
Touch down: Kim arrived at LAX airport on Friday in Los Angles
While in France, she attended the premiere of new beau Kanye West's short film Cruel Summer.
The 30 minute movie, inspired by West's upcoming G.O.O.D. Music compilation of the same name, plays like an extended music video.