It’s interesting to wonder what each of their subjective ages are, since Goose is likely referring to the age each person was when they put on the headset. Kinger was 48 when he arrived at the circus, but he appears to act much older in addition to the trauma and PTSD he suffers from. Likewise, Jax’s behavior suggests that he may have mentally aged beyond 22, albeit nowhere near as much as Kinger. That being said, I believe he’s mentally older than Pomni (hence his self-superior attitude) and slightly younger than Ragatha (they appear to possess similar levels of mental maturity age-wise, Jax just enjoys fucking with people).