Kris Jenner admitted the biggest mistake in her life was being unfaithful to her ex-husband. Kris spoke out about her infidelity that occurred while she was married to Robert Kardashian, Sr. for 12 years. "What was your mindset when you cheated?" Khloe Kardashian asked her mother on yesterday’s episode of "The Kardashians" on Hulu. “When you did that with my dad, and you had four kids and you had a family? … Yes, I know you were really young...." Jenner replied, "…being really young and dumb is something that plays into it because you don’t really understand the consequences of your actions." Khloe dug into the conversation deeper and asked, "But what was my dad not doing that made you want to look elsewhere?" Kris said: "I don't know because he was such a great husband and such a great dad… I think that I fell into a situation where I thought that the grass was greener somewhere else, and I made a huge mistake. That’s my life’s biggest regret." Kris and Robert were married from July 1978 to March 1991.