Rehau is located in Tanna, Wilna, Rzgow, and Bucharest at the same time? ;) But yes, it belongs to Veka.
You are confusing that with Gealan/Veka. Gealan, among others, produced in Oberkotzau. After the takeover by Veka, if I remember correctly, some production was relocated to Veka sites and more focus was placed on development at the Gealan headquarters. Oberkotzau is in the district of Hof, just like the city of Rehau, where the company Rehau AG & Co has its headquarters. However, no window profiles are manufactured in Rehau. Products for the industry (edgebands, magnetic seals) and the automotive sector are produced there. Otherwise, the main administration and research/development are located there. Rehau itself develops the profiles including the associated production technology. Either for small window manufacturers (e.g. Synego) or as OEM for the big companies (e.g. Weru). The production sites for window profiles that I personally know of are Wittmund (DE), Srem (PL), Gschel (RU), Blaenau (GB), Poix (FR). But there are many other locations worldwide. Some of them also produce window profiles, usually variants for the respective window construction type.