It is generally imagined that this occurs most often in families in which the parents speak different languages, and meet and fall in love at Esperanto congresses. While there are many of those families, most often both parents have the same native language. In that case one of the parents, usually the father, chooses to use Esperanto with the children in order to enrich their native knowledge and experience.
As with all children who speak a language that is not the mainstream one in their culture, it is extremely helpful to meet regularly with other native speakers. It is therefore important to the language skill of native Esperanto speakers if parents regularly bring their children to Esperanto conventions. The annual Children's Congress of Esperanto (Infana Kongreseto) happens alongside the largest Esperanto convention, the World Congress of Esperanto (Universala Kongreso).