Hi Isabela!
Most of the crew is in their early 30s. Raelan is 26 in the beginning of the game. Argandea's race lives a little longer than humans, so his human age is more or less closer to late 30s in the first game. 40ish in the final season along with Theo being the oldest 41.
But I know age can sometimes be a deal breaker in terms of immersion, so please feel free to imagine them any age you like!