Television personality Kris Jenner, who is also the manager of her children's career, says her eldest daughter Kourtney Kardashian, is the toughest to manage.Host Andy Cohen asked Kris during the "Keeping Up With the Kardashians" reunion: "Who's the hardest (to manage)? Who gives you the most lip?"Kris said it was Kourtney, adding she could be stubborn and difficult to deal with.She said: "I don't want to do things if it's not something I'm really into doing. My answer is no for most things and if it's gonna be yes, I want to know every detail of what I'm gonna be asked of."Kris shared that model Kendall Jenner is her easiest daughter to manage, and Khloe Kardashian says that her mother deserves all of her success, reports femalefirst.co.uk.She said: "Our mom works so hard and no one, especially at the beginning, did believe in us the way that our mom did. She really just knew that we can do all these things and my mom is giving us our careers, or helping us navigate through that and it's only fair that she gets paid for that."