​In a group of four people, A is older than B, D is younger than B and C is older than D but younger than B. Who is the youngest among all? ​

From the  given the following relationships based on age:

A is older than B → A > B

D is younger than B → D < B

C is older than D but younger than B → D < C < B

Now, we can rank their ages based on the given information:

A > B > C > D

D is the youngest among all.