dataset.merge with itself-create multiple records with same values

I am trying to create a dataset with multiple records that hold identical
data by merging a dataset with itself. I don't think this will work and I am
looking for other solutions.

For example, a dataset has a parent table called CATEGORY and a child table
called ITEMS. There is a foreign key column and the value is -1 for the
parent (and child refers to row -1). Now I want a dataset that has 3 records
with this same information. I want row -1, -2, and -3 all with the same
values. I don't think Merge is what I am looking for because when the dataset
tries to merge with itself, the primary key of -1 is the same and instead of
adding a new row with primary key -2 it merges (imagine that) which results
in still only one row. Does anyone have a better solution to this? Otherwise
I need to manually create all the tables and rows by looping through the
original dataset. Thanks.