The desired functionality is not available out of the box in the Kendo UI Grid.
A similar result can be achieved using custom logic for sorting the items using the custom compare function. The logic may be applied that regardless of the sorting direction the both rows will always be displayed on the top:
Still, the desired result can also be affected by filtering, grouping, paging and other functionalities of the Grid which can cause unexpected issues.
I can suggest submitting a feature request for having frozen rows, and based on its popularity we may implement in as a built-in feature in a future release.
Telerik by Progress