Question: who became king of erebor after thorin dies?
Answer: Dáin, his cousin Dáin

When Thorin died , he was buried with the Arkenstone , and Orcrist was returned and laid upon his tomb . The blade would glow blue should Orcs approach , and they could thus not take the Mountain by surprise . Thorin was succeeded as leader of Durin 's Folk by his cousin Dáin .