I pretty much shipped Ur and Silver since he was first introduced; come on, admit it. Both fight with ice, and both are like Gray's guardians, so it's like the perfect match!
But then I started doing some digging on the ship to look for art, and I came across this theory. After reading it, I was pretty much like Well holy hell, my ship could be real. A lot of things stated do make sense on how Ur could possibly be Silver's wife. So after a bit of thinking on the subject and piecing some things together, I've elaborated on the theory, with some points brought up there, and with some of my own.
Ur abandoned her husband for an unknown reason sometime before she had Ultear. It's actually very likely that she and Silver were married, and that she left him because he was evil. Think about it: Silver is fighting on Zeref's team now. He might've been on his side the whole time.
Ultear was born with far too much magical power. Not to mention, she has ice magic. Being the daughter of a mage as powerful as Ur and an ice-devil slayer, it would be no surprise that she was so ill as a child.
When taken to be healed, there's a good chance that Silver knew Ultear was Ur's and his daughter, and he could've played a role in her abduction and corruption.
Why would Silver pretend to be Deliora?
Well, Silver knew that Ur sacrificed herself to defeat Deliora and ultimately, to protect Gray, his son. It would be so much easier to kill the one who was responsible for his wife's death if Gray didn't know that he was fighting his own father.
Silver wanted to see Gray dead. Basically, if Gray is responsible for Ur's death, then Silver wanted his own son to suffer.
That would explain why he attacked him so viciously, and why he constantly brought up points about Ur. He wanted to see Gray cast Iced Shell to kill them both. Perhaps he didn't want to live anymore without his one true love?
He wants to kill Ur's pupils for having a life with her, perhaps like he's always dreamed of? Silver probably didn't want to leave her; he would've been envious of her students, and of their daughter. Perhaps that was also why he helped bring Ultear to the dark side, so Ur would lose everything like he did.
How did Silver know that Lyon was also Ur's student? He and Lyon never associated, and he wasn't involved enough in Gray's life to know that he and Lyon were close.
He might've observed Ur after she left. We don't know if he was there in the background, watching everything unfold.
So why do Silver and Gray have a father-son moment? Well, Gray and Silver are father and son. They would've been close when Gray was a child because Gray hadn't gone to live with Ur yet. Basically, while Silver loves his son, he's also both envious of and furious with him for having the chance to live with Ur, to be someone she treasured, and for being the very reason she sacrificed herself.
There are still a lot of things that don't exactly click, I guess, but this is my take on it so far. For instance, Silver didn't have his ice devil slayer magic when he would've met Ur, or did he?If anyone questions it, I'll definitely rethink these things and try to elaborate it and make it seem more real. Thanks for reading! Love this ship~