Use Custom People Fields
Enabling this feature allows you to add custom fields to Households and People (address, email, group name, anniversary, etc).
Step 1: In your Admin > Settings tab, click the checkbox next to "Use Custom Fields" and click "Save Settings".
Step 2: You will see a (Manage) link appear next to "Use Custom Fields". Click it to add/edit/delete custom fields for households, guardians and children.