Answer
(Fatwa: 1269/1083=L/1429)
If there are only the abovementioned legal heirs of your elder brother then after paying all due rights preceding the inheritance, the wealth of your elder brother will be distributed in 24 shares, out of which 3 shares will go to wife, 4 to mother and 17 share will be given to his son.
Note: If your father is also alive or your elder brother has any other heir (not mentioned in the above question) then ask the question again and consider this reply cancelled.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband