Typically, Systema is not taught to children under 3, but a parent may start to teach a child Systema from the moment they are born. Anyone who has paid much attention to a newborn’s breath knows that for the first few months of life, babies breathe in cycles, progressively becoming quicker and deeper and then slower and shallower. A child’s breath needs to mature and develop through practice, physical development, and imitating its caregivers.
As you practice daily, your child will notice how you breathe, how much fun you have rolling on the ground, doing sit-ups, push-ups and squats. There is no need to teach them; they will get down next to you and explore it themselves. Your example is enough.
Adults learn by example as well. Through videos, instructors, and peers, adults learn by observation. Often there is no need to “teach” because words will just get in the way.
For more information on teaching Systema to Youth, see Konstantin Komarov’s article “Kids in Systema”