Though I don't know if I see Fai and Ashura having a parental/son relationship, personally. While it may not be romantic, it doesn't really seem to have that dynamic to me.
It could be a mixture of parent-child and romantic - it's not like CLAMP hasn't doen that before. Fai could have had romantic feelings for Ashura-ou while Ashura-ou thought of Fai as his son, for example. Or it could have been a relationship that started more familial (or resembling familial) and became romantic. You never know.
I agree with previous posters on that Fai and Ashura's relationship could possibly have gone from family to romance. I'm thinking of that splash-page showing them together; although Fai resting in Ashura's lap could indicate parental/childish love only, the text that accompanies the pic could not, at least not to me. I don't remember the exact wording though - anyone?
A little off topic, perhaps, but you know what strikes me looking at those sketches? Everyone is drawn together with an (arguable) father figure (and, in the case of Kurogane, a mother figure as well), but why is little Sakura being cute together with Touya and Yukito instead of Clow? I mean, it's no secret that he is her father. Mysterious guy... I bet he isn't even dead.
A little off topic, perhaps, but you know what strikes me looking at those sketches? Everyone is drawn together with an (arguable) father figure (and, in the case of Kurogane, a mother figure as well), but why is little Sakura being cute together with Touya and Yukito instead of Clow? I mean, it's no secret that he is her father. Mysterious guy... I bet he isn't even dead.I dont think they really needed to be parents I think it was just a childhood thing, Kurogane, Syaoran and Fai(?) didnt have older siblings. I'm not sure if it was father figure so much as who took care of them and raised them.