Is the snake guy the brother? He and doram look a lot alike

Why would Do-un be an ancient snake spirit though? Also the goblin boy turned the snake into a human, if that was Do-un, why would he need to hold the bird hostage for that? The goblin is already on Doram's/Do-un's side and could've turned him human as a regular favor.

I think it's just another case of a generic uke face.