TRC Chapter 170 **SPOILERS**
Holy shit! Just read Chapter 170 and while reading it, something occurred to me when Seishirou was saying that that Syaoran is so very like his father in that respect. He was saying it about watching through his link with his other self. Watanuki could be that other self of Syaoran's father or Watanuki is Syaoran's father and Seishirou was referring to Watanuki seeing the world through his other self that he created with his dreams.