Victorian brain teaser, sadly no prize offered.

[High Wood]

This picture represents a classic slice of Victorian sentimentality. Taking it as read that the original picture was painted from life and that everything seen in the picture was there at the time of the painting, i.e. that there was no artistic licence involved, can someone please tell me the youngest age that the veteran could have been when it was painted?

I would like to have a possible age and more importantly, the reasoning behind your answer.