Ryland Grace is not given a specific age on Erid in the sources I found. The book’s ending leaves him living there with Rocky, but it does not pin down an exact age at that point.

What can be said is:

  • He spends years on Erid after the mission succeeds.
  • The epilogue shows he and Rocky remain together there, but no exact birthday or age is stated.

If you want the closest canon-based estimate, the story only supports a rough timeframe , not a precise age.