Why do domestic automobile joint ventures have two companies under one brand?

Joint ventures are shrewd in cooperating with Chinese automobile manufacturers. They will hand over different types of automobiles to different Chinese companies in order to obtain maximum profits and voice. For example, Volkswagen not only has Audi and other models with FAW, but also has a joint venture with SAIC to produce Passat and other models; Honda has GAC Honda's Accord series and Dongfeng Honda's CRV models. As market rules change, they also have an integration problem. For example, Ford has made attempts in this regard, but in most joint ventures, each model still belongs to its own owner.