Oblique case... or not.
Namaste! I have a problem. The task was to pick up the correct form of the adjective:
(uska, uski, uske) bhai dusre sahar me hai
(I guess it means, His brother is in another city).
I´ve chosen the variant uska, because bhai is masculine (nominative)
dusrE sahar me - oblique
But the key answer says, there should be uskE. I can´t understand why...

Question

Oblique case... or not.
Namaste! I have a problem. The task was to pick up the correct form of the adjective:
(uska, uski, uske) bhai dusre sahar me hai
(I guess it means, His brother is in another city).
I´ve chosen the variant uska, because bhai is masculine (nominative)
dusrE sahar me - oblique 
But the key answer says, there should be uskE. I can´t understand why...

Answer

Uska bhai dosrey shehr mein hey.
His/her brother is in another city.

Uske bhai dosrey........

His/her brothers are in other city.

Plural of bhai is bhai.

in my opinion both are correct.

I hope it helps.

Answer

correct sentences are: 
1. uska bhai dusre shahar me hai.
2. uske bhai dusre shahar me hain*.
if key says answer "uske" then sentence must end with "hain" and not "hai". please make a note of it. Either your question on spelling "hai" or he key is incorrect.

Answer

the * key

Answer

Uska bhai - is for brother of almost same age
Uske bhai - is for his elder brother(here "Uske" is with respect)
like 
Uske Pitaaji, Uske Uncle, Uske Teacher
Uska bhai, Uska dost