"Hvorfor lyttede du til bror?"

Translation: Why were you listening to your brother?

[MusicWithRocksIn]

Does this still make sense? There is another sentence "Hvorfor lyttede du til din bror?" which is apparently translated the same way, but I feel that the din part is quite important.

[AleksBromvig]

You are right. This doesn't really make sense. The translation would be "why did you listen to brother?", which would only make sense, if you had a person you specifically called "brother" (like you could say "why did you listen to mother?" if you were talking to someone in your family).

[MrGusts]

Yes, "Why did you listen to brother? " should be accepted.