User blog comment:Omega natsu2/Chapter 367: Jellal vs. Oración Seis, Predictions./@comment-190.172.188.65-20140113050538/@comment-24066070-20140113084836

Perhaps Gray is a half-demon thanks to Silver being his dad. Deliora spared Gray, because he recognized a fellow demon. Silver hates Gray, cuz he came forth from a "forbidden" love and cuz he sides with humans. In short, he can't stand his son (who should've never been born in the first place) siding with humans.

At the end of the Arc, FT will be forced to kill Gray due to his demon heritage.

This is how I want things to unfold!