If you have a relationship between parent and child that works why duplicate parent data in child records?
You should really think about data structuring and normalization.
ok, thanks will read through it and come and see, i really appreciate this
it was not duplication perse( as i understand it)
in the new layout i did not was to manually type the surname again since is the same as parent
currently is blank
the next layout will be customer list with parent and child on different rows
You may want to have Parent and Children in the same table with a name like Person and then use different table occurrences for Parent and Child. It will make it easier to show all of your customers together.
I would look at using a portal of the Child table occurrence on the Parent layout to add children to the parent relationship.
Now to your original question, one way to populate those fields is it setup a calculation on your text fields that will set the initial value as the same as the parent record. So the formula for the last name field would be "Parent::Last Name". By using the text field with a calculated value it will still let you change the data on the child record when you need to change it.
Another thing to think about is how are you going to relate the one child to two parents. Or from my experience maybe four parents.