Traditionally the requirements for an independent state is that it have control of it’s own territory, it have a permanent population within it’s territory, it have a working government and have the capacity to enter into relations with other states. From this point both Republic of China (RoC) and Peoples Republic of China (PRC) are independent states.
There been a change to this ruling in modern time and it’s that a new country formed as sub-set of an existing state needs to have the mother states blessing and here is the problem for PRC, they never have had the blessing of RoC to form a new state, as there ain’t any peace treaty between RoC and PRC.
This leads to that PRC isn’t a state of it’s own, but a state within RoC that do not follow the constitution of the RoC. Even if a member of UN, PRC do those not technically exists and is just a territory lead by a terrorist organisation (CCP) much like Daesh (ISIS).
So there is just one China and it’s the Republic of China, most commonly called Taiwan.