"It is the way Clow made me. At the very end of my cycle of creation, he put a binding on me, intending to make me loyal to all his descendants:

'...and as the Moon is drawn to the Earth, thou shalt forever be drawn to those of my blood. An they have magic and blood of my line in their veins, they will pull thee, be irresistible to thee. Thou shalt follow them as the Moon does the Earth...'

"But he did not take into account the corollary effect, or the fact that magicians can always be bound by their own magic."

-Yue, quoting Clow Reed -A Matter of Trust - a fanfiction by Sparkle