"It's a boy!" The midwife busted into the room. Thorin and his brother-in-law have been waiting for the birth of his sisters first born.
"A boy! How bout that Thorin?! I have a son!"
"Yes. It's very great indeed." Thorin said.

They went into the room Dís was in. She was holding a small baby with blond locks. He was the perfect child. He hardly cried at all.
"I want to give him a Durin name." His brother-in-law told him.
"What? Don't you want to give him a name from your family?" Thorin asked him bewildered.
"He will still have my last name. He has better things to live up to on his mother's family. He will be a great king someday."
"It's not certain yet. He might not be king." Thorin said. Thorin was still hoping he'd find his one and have his own heir. But him being so old it seemed unlikely and he was beginning to lose hope.
"Fili. Fili Arkin." Dís said.
"You're naming the child after me?" Thorin asked even more shocked. His middle name was Fili. Thorin Fili Oakenshield.
"Yes. I couldn't think of a better man." Dís smiled.
"I feel like I'm stealing your child." Thorin said to his brother-in-law.
"Nonsense. He just needs someone like you to look up to." He said.

That night Thorin was holding the child. His mother and father were sleeping so Thorin had some alone time with his nephew. He stared into the child's glowing eyes. He already had the features of a king. Thorin knew he would be a great king. He made up his mind right then, this child, Fili Arkin, would be the next king of Erebor.
"I swear to you Fili I will reclaim Erebor for you. You will see your home and you will rule it." He promised him. And he intended to keep that promise....even if it was the last thing he did.