How is Clow Reed and Fei Wong Reed related in Tsubasa Reservoir Chronicle? Considering that Clow Reed and Fei Wong Reed have the same surnames and that they both have magical powers, how are they related? It was not clearly stated on the anime series and the manga on how they are related (Or I just overlooked it?). Are they brothers or relatives? Or they just coincidentally have the same surnames? (Though, Yuko said that there is no such things as coincidence, there is only inevitability.) 

I'll appreciate any details. Thanks a lot.
According to the Tsubasa Wikia:


  Fei Wong Reed also mentions Clow quite frequently, and he's also a descendant of Clow.


This is shown in chapter 64, which appears in Volume 9 of the manga. He is described as somewhat of a distant relative of Clow Reed.

Information for this can be found on: Fei Wang Reed's Wikia page and Fei Wang Reed's section on Wikipedia. The citing is provided on the Wikipedia page.