`KHF_(2)` exists while `KHCl_(2),KHBr_(2) ,KHI_(2)` do not-why?

Explanation

The fluorine atom (F) or fluoride ion `(F^(-))` has a strong tendency to form hydrogen bond owing to its small size and high electronegativity. Hence, when KF is added to liquid HF, the `F^(-)` ion of KF combines with HF through hydrogen bond giving bifluoride ion `(HF_(2)^(-))`. Hence, `KHF_(2)` exists. However, a relatively low electronegativity and large size of the other halogens, prevent the formation of `HX_(2)^(-)`. Hence, salts like `KHCl_(2)KHBr_(2)` and `KHI_(2)` do not exist.