That’s the username you set up for them when you created their account. When logging into Origin, you need to use your child’s EA ID instead of an email address.
Access to these features depends on the game and platform, as well as the parental controls that have been set. This is to ensure players under the minimum age in their country have an age-appropriate experience. Child accounts may not have access to certain features like online multiplayer modes, purchases, and social media connections.