Teenager A: I found an interesting relation between my age and the age of my father. Multiplying my age by the age of my father I get the same result if we use the correct ages or if both of us reverse the ages' digits prior to the multiplication.
Same happens if I do it with my grandfather's or even with my aged grand-grand father's ages.
B, A's brother:
That applies to my age as well.
C, a friend: My age, too. But no grand-grandfather...
All the ages (A,B,C) are distinct.
What are they?