Based on the English alphabetical order, three of the following four letter-cluster pairs are alike in a certain way and thus form a group. Which letter-cluster pair DOES NOT belong to that group?
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Logic: 1st letter + 7 = 3rd letter and 2nd letter + 7 = 4th letter

Now, we check each options.

Option (a): PU:WB (Follow)

P + 7 = W, U + 7 = B

Option (b): AF:HM (Follow)​

A + 7 = H, F + 7 = M

Option (c): KP:RV (Not Follow)​

K + 7 = R, P + 7 $$\neq$$​ V

Option (d): TY:AF (Follow)​

T + 7 = A, Y + 7 = F

Thus, correct option is (c).