بسم الله الرحمن الرحيم
(Fatwa: 779/719/N=1434)
In the question mentioned above, if you have not absolved your brother from the loan then its zakah shall be wajib on you each year. However, it shall be wajib on you to pay it after you receive the amount. However, if you pay its zakah each year without waiting to receiving the amount back then it is also alright.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband
