'KUWTK' Kris Jenner Cries To Kim Kardashian: Admits Worry Over Rob, Khloe Kardashian (VIDEO)

Kris Kardashian lies awake with worry for her children every night and when she thinks of son Rob, she cries herself to sleep.

In this week's preview for Keeping Up With Kardashians, the momager reveals her concern for Kim's baby brother and his struggle with depression and weight gain, while on a vacation with the family in Thailand, which Rob did not attend.

In an episode that airs this Sunday, Khloe is also unhappy on the trip and wishes to go home. Words are exchanged between Kim and Khloe, and in the clip Kim discusses the situation with her mom.

Kim says of Khloe, "It's like she gets anxiety with the whole Rob situation when she's away. I just don't see what the point is. She doesn't need to help everyone."

Kris is sympathetic to Khloe and tells her daughter, "I want to fix Rob and sometimes you just can't. I have not not cried myself to sleep in so long that I don't even know what that's like. It's the worst feeling in the world when one of your kids isn't in a good place.

"You don't think it's torture for me to be here in Thailand and have him at home?"

While Kim lends a sympathetic ear to her mom, that's as far as she goes. She tells Kris that as far as Rob is concerned, "We've all been here to offer him help and he won't take it, so I don't have sympathy.  I think I'm just more of the tough love kind of person. My personality is like, 'All right, you complain, you don't like it, get up and do something about it.'"

Check out the revealing exchange below:

Viam E! Online