User blog comment:FairyRaven/Fairy Tail Chapter 387: Tartarus Arc, Part 4: Father and Son, Review and Commentary/@comment-5268982-20140606181923/@comment-5268982-20140606182532

I think there is only a slim chance for Silver to be Gray's dad. Consider the following; has it ever been established in the series that a parent smells like their children? No, not once. Not with Jude and Lucy, and certainly not with Cana and Gildarts. That's why Natsu and Gajeel cannot explain why Gray and Silver smell the same.

My best guess is that they're the same person, or maybe twins? Idk