Foreign Key not updating

I cannot work out why child record will not save foreign key.

Visual Studio 2010 Visual Basic

I have 2 tables in table 1 primary key is ID and in table 2 foreign key is ID

I have then created a dataset and from Solution Explorer and added Relation Only (Key Columns ID and Foreign Key Columns ID)

Then dragged a DataGridView from the dataset to my form for the Parent table and then dragged a DataGridView for the 2nd table (selecting the table from within the first table list through the DataSources window)

When I add the first record to the parent table, the 2nd DataGridView correctly entered the foreign key at -1

and if I add a 2nd record to parent, enters -2 and so on

but when I save, it is saved as -1 (-2...) rather than change to the actual primary key ?

I cannot understand what I have missed ?