She had a tragic break-up when Bruce Jenner the ex husband confessed to be transgender woman and changed his contact information including his name to Caitlyn.
Kris is content with the life she's having with the boyfriend and doesn't need any label (marriage) to define it.
Seems like marriage is not part of the plan for these two at the moment, despite the age difference of 25 years, they are still dating and no one knows up to when.