You can create a pivot table from two or more data sources, as described
here:
http://www.contextures.com/xlPivot08.html
but the results are not the same as a normal pivot table.
Also, if the pivot tables have multiple row fields, there will probably
be many blank cells in the outer fields, because headings are not
repeated on every row.
If possible, combine the source data on which the two pivot tables are
based, and create the new pivot table from that data.