There is a lot of collabaration between manufacturers but JCB aren't associated with Cat as far as I know.
JCB were working with Japanese manufacturer Sumitomo to build the original JS range but once they were ahead of the game they severed the tie and are now working alone.
I think Sumitomo are working with Linkbelt and are linked through the CNH group.
Someone may have better insight but I think Cat were working with Mitsubishi and now have some association with O&K after their bad experience with building their own mining shovels.
Volvo were working with Ackermann but purchased Samsung and that's what their mainline excavators are based on.
Komatsu work independently but purchased Demag to acquire large shovel technology.