It is not unusual for RV manufacturers to sell parts to each other, when one has a manufacturing capabilities the others lack. Or they could be using the same third party supplier.
Practice follows that of the auto industry. In the late 50s and early 60s Chrysler was making seats and interior trim for AMC, and parts like steering gear, air conditioning and transmissions were bought from the same third parties or sold across corporate lines. Sometimes even engines were sold, Studebaker and AMC (and later Chrysler) buying engines from Chevrolet and Pontiac divisions of GM.
Tom Test
Itasca Spirit 29B