NH3 will form NH4+ in water.
There is an equilibrium: NH3 + H20 <--> NH4+ + OH-
The pH will be >7, because NH3 accepts proton from water forming ammonium hydroxide solution (weak base).
You need to understand that KOH (potassium hydroxide) is a strong base, and will dissociate completely. This will drive the OH- concentration higher, increasing the pH. This shifts the equilibrium towards the formation of NH3, depending on the amount of KOH.
NH4NO3 (ammonium nitrate) and NH4Br (ammonium bromide) are weak acids.
KBr forms a neutral salt solution.