It's a magical world

I can understand the doubts of many fans about Parents|SxS and also how wonderfully convenient, plot wise, it would be for them not to be the CCS|SxS but better to be actually the reincarnated clones from TRC, it would explain quite well why father and son looks exactly the same...but still, you are forgetting an iron clad sentence repeated enough by both Yuuko and FWR for us to remember it for a lifetime: "Syaoran is Clow Reed blood related relative", having inherited those powers mainly from his father's side, who is a Li. Starting from the point Clow Reed was undoubtedly recognized as being the same as CCS, they can only be CCS|SxS since they are the only ones who could have given birth to someone who could be said related to Clow Reed through blood ties.