The brothers did not anticipate the company of another dwarf so soon after leaving the mountains. And yet when Bilbo comes in and motions to person behind him to come in as well they are at a moment of complicated feelings.

Fili is glad for the presence of his kind. Being the only dwarf besides Kili in the whole Hobbiton is tiring, and even though Bilbo is amazing and they love him to bits, he's not a dwarf, and doesn't know all their customs yet, not that he isn't slowly learning. So he smiles at Bofur as he is introduced, exchanges a few greetings in Khuzdul with him, and slams his hand on his shoulder in welcome.

Kili is suspicious. He thinks that this newcomer stands a bit too close to their Auntie, and smiles a bit too widely at him. He does keep his hands to himself though, so that saves him a few broken fingers.

Bofus just smiles, happy to be at a friendly person's presence.