WPF:将GridView头分割为两行，其中底行被分割为两列

I´m trying to separate a gridViewColumn into two rows. Im using default style for the listView. Its no problem to separate the column header into two rows, but it seems like the content is placed over the original style with the border etc hidden under my customized gridViewHeader content. The code looks like:I´m trying to separate a gridViewColumn into tw