Board Thread:Questions and Answers/@comment-9964494-20141106031052/@comment-679780-20160927134205

True ages of the characters:

Sonic- 15 Tails- 8 Knuckles- 16 Amy- 12 Shadow- Unknown (Pressumed 50+) Rouge- 17 E-123- Unknown (Pressumed E-series creation) Big- 18 Cream- 6 Vector- 20 Espio- 16 Charmy- 6

These ages are confirmed in the Sonic Heroes manual.