Translation:Is the younger brother short?
I think "Is your little brother short?" should also be accepted, given that "弟弟" does not contain a possessive particle and could be inferred to be the listener.
As a native I would not omit 你 if I talk about the brother of the listener.
Would you ever ask this question though if you were not talking about someone's specific younger brother?
If I talk to a person outside my family about my own younger brother, I will need to say 我弟弟 or 我的弟弟.
"我的弟弟矮不矮？ " is a valid question if I want someone, say a peer, to give that judgement.
A possible scenario is, 2 sisters talking about their younger brother who fails to get a date.
The audio is butchered when it pronounces the whole sentence. It seems to always pronounce "矮" in a choppy way in a whole sentence. I reported it.
Correct pronunciation is
didi ai bu ai
What I heard is
didi dai bu yai
I think it is probably a problem of recording quality? I am now a bit worry about the sounds in the Korean course... I have no idea what Korean sounds should be like.