Am I reading this correctly; you want the parents contact information, i.e. phone number, address, etc., also entered into Fields in the child's record?
If this is your intent, go into Properties - Data of the Subform Control and add/link those Fields, as well as the ParentID field.! You're not limited to one Field when linking the Form/Subform, you can enter multiple Fields.
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007