How old are Sonic Sonia and Manic?

Since at the time of Sonic Underground's creation and the fact they are animated in the style of the old 2D Sonic games. It is safe to say that Sonic, Sonia and Manic's age is 10 as they are triplets and Sonic's age was not changed to 15 until his character was redesigned, so only his redesigned form, as the one we know now, is 15 years old.