Kinect 2 uses Time of Flight developed, as far as I know, by Microsoft.
https://www.gamasutra.com/blogs/DanielLau/20131127/205820/Th...
The core technology (structured light in iPhone X and Kinect 1, ToF in Kinect 2) is rather straightforward (for a computer vision researcher, that is...), it's hardware (embedded CPU, cheap sensors and lasers) that enabled its mass adoption.
They produced an ASIC that ran the structured light system, as well as a custom grating to produce a very specific light pattern.
Xtion was a Primesense ASUS partnership to bring the tracking technology to the PC.
Xtion was not a separate company but rather an ASUS branded Kinect-like sensor.
Primesense made the sensors for both Kinect and the Xtion.[0]
Primesense was later purchased by Apple in 2013.[1]