Kris and Caitlyn Jenner stay ''cordial'' for the sake of their daughters.

The 'Keeping Up With The Kardashians' star may have had a difficult split from the former athlete - who was known as Bruce Jenner before undergoing a gender transition - but the pair remain civil for their kids, Kendall and Kylie Jenner.

A source told People magazine: ''Kris and Caitlyn interact when they have to for the kids. It's important for Kylie and Kendall. They can be cordial, but like most exes, they're never going to be best friends. Things are still frosty between them. There are too many hurt feelings between Kris and Caitlyn and the older girls. It wasn't a happy, laughing interaction between Kris and Caitlyn. It was more like, this is a moment where we're coming together for the kids. It was very brief.''

Meanwhile, Caitlyn previously admitted she finds it ''tough'' maintaining a relationship with her children - Burt, Casey, Brandon, Brody, Kendall and Kylie.

She said: ''I spend a lot of time by myself here in the house. I have a lot of children, but sometimes just because of circumstances, maintaining a close relationship with your kids is very tough. They all have lives. They've all moved on. We're just human beings; we're going to be here for a very short time. We come and we go and at the end, when it's all said and done, hopefully your family is going to be there.''