User blog comment:PUNCHURPREGNANT/Gray and Silver Predictions/@comment-1478718-20140114003501

I think Silver is Grey's father. Hear me out:

They look alike but not identical- Silver's features are similar to Grey's although their eyes are different. They could easily pass as close relatives, and Silver's apparent age puts him at the right age to be Grey's father. (Remember that despite Grey looking like a teenager, he is fact 25/26 years old due to Fairy Sphere)

Grey melts the ice freezing Atlas Flame. He does this by manipulating the magic itself. Earlier when fighting Doriarte, he was able to siphon power out of the ice, not just energy, but the essence of the magic itself (effectively wielding Devil Slayer magic) to defeat Doriarte. On a different note (highly circumstantial evidence here and possibly disproven by the anime when they get there), Grey's ice looks similar enough to Silver's that Doriarte wasn't able to tell a difference when Grey was creating traps against him. Remember that Grey, Lyon, AND Ultear have a different color tint to their ice magic in the anime, being light blue, light green, and purple respectively. Grey and Lyon both learned there magic under Ur, so you would think their magic would be the same in color. Ur's is very similar to Grey's when seen in the show, although Grey's ice has gotten more of a blue tint over time.

Also there is the fact that Natsu remarked on Silver's scent. We don't know just how alike they smell, but their scents are similar enough for Natsu to remark on it. Remember Natsu sees Grey on a near daily basis and aside from Happy and Lucy, Grey is his closest friend. He would be very familiar with Grey's scent.

Grey and Silver have similarly themed names, which could be coincidence, but remember how often themed naming is used IN UNIVERSE in Fairy Tail. Lucy's name come from the sign of the merchant guild where her parents met. Erza was named after her red hair. Ultear's name came from the tear's her mother Ur shed. It's very possible Grey was named in homage to Silver.

My current theory is that Silver is possessed/merged with one of Zeref's demons. I think Silver learned Devil slayer magic to kill Deliora, after the death of his wife and as far as he knew his son. Eventually, he was found/captured by Tartarus and turned into one of the Nine Demon Gates.

Because of this he still has the man's sentimentality as well as his crusade, but despises anything that might make the human part of himself grown strong enough to effect him.

By the way, say what you want. Grey is my favorite character in Fairy Tail.