It depends on the individual boy. Some boys started when they were three.
You short start with karate if you have never done any kind of martial arts before.
"Martial arts begin and end with courtesy" - Mas Oyama
Martial arts predates written history.
Mixed Martial Arts is martial arts, which should be obvious from the name. Over time all martial arts are very similar. While they start with different focus, they eventually blend together, as the human body can only move in a limited number of ways.
Martial arts is a violent past time and children should not practice it.
Mixed Martial Arts Champion and youngest person to win a black belt continuous fighting title
the Arni's Martial Arts have a rattan stick. while the other martial arts have no weapon
It is your own decision
Given clearance by your doctor, there should be no problem. Contact fighting may be off the list, but you can still participate in martial arts.
Martial Arts refers to the skills used in combat. Every country has martial arts and some originated in Japan, but not all of them.
The first step would be to learn a martial art. Then you can take it to the next level.
All styles of martial arts do.