Single word for for "beyond their years"

Is there a word that indicates somebody has an innate sense of something exceeding the expected grasp of that sense for his age? Similar to wise beyond their years.

An example case would be a ~18 year-old teenager that is as mature and responsible as an average 35 year-old adult.

The death of his parents early in life had instilled in John an X sense of responsibility for his younger siblings.

I keep thinking of "preternatural", but I feel like it's too broad. You could use it for things that are too big, too fast, or just plain unusual. I'm looking for something that deals specifically with time.

Solution 1:

My first thought was advanced as his sense of responsibility is advanced for his age:

advanced

ADJECTIVE

1. Far on or ahead in development or progress.

   ‘negotiations are at an advanced stage’

(from the Oxford Living Dictionaries)

so you would say:

The death of his parents early in life had instilled in John an advanced sense of responsibility for his younger siblings.

but that doesn't really give you the full sense of beyond his years, so I came up with premature as he has certainly been prematurely forced to grow up:

premature

ADJECTIVE

1. Occurring or done before the usual or proper time; too early.

   ‘the sun can cause premature ageing’

(from the Oxford Living Dictionaries)

This would make your sentence:

The death of his parents early in life had instilled in John a premature sense of responsibility for his younger siblings.

Solution 2:

Although it's often used somewhat back-handedly, this is the literal meaning of precocious:

precocious adjective 1. unusually advanced or mature in development, especially mental development

source

When used literally it most often refers to advanced intelligence, but it can also refer to other signs of advanced maturity.

In your example, you'd say "John has a precocious sense of responsibility".