Actually it's a little bit more complicated: the appliances are made by a company called BSH (https://en.wikipedia.org/wiki/BSH_Hausger%C3%A4te) which was originally (since 1967!) a joint venture between Siemens and Bosch, but Siemens withdrew from it in 2014, and since then it's a fully owned subsidiary of Bosch (but still uses the Siemens brand as well as some other brands such as Gaggenau, Neff, Thermador etc.).

Bosch owned Junkers since before WW2, at least heating appliances, I think airplanes where independent. They started rebranding Junkers to Bosch Thermotechnik ~20 years ago. I think they never sold heating appliances in UK under Junkers brand.

That has become common now in all industry - for example, in India, Bosch refrigerators uses compressors manufactured by Godrej (an indian company). So their indian fridges aren't exactly "German engineering", unlike their washing machine and dishwashers that are made in-house. LieBherr, another famous Swiss German brand, on the other hand has their own factory to make the refrigerators in-house in India, but their service in many cities is outsourced to one run by Bosch + Siemens (plus one more group I can't remember).