I saw the documentary on TV. Perhaps a NOVA piece. Here is a pharaoh list with Seti 1 and Seti 2 in the 19th Dynasty. I believe the reason suggested by the TV piece was his wish to emphasize the importance of the Rammesid line of rules. This list does include the folks that Seti tried to eliminate.
http://www.metmuseum.org/toah/hd/phar/hd_phar.htm
Haremhab wasn’t connected to the 18th dynasty.
http://www.varchive.org/tac/hararch.htm
Seti, Ramses:
http://www.varchive.org/tac/sethos.htm
http://www.varchive.org/tac/3br.htm
http://www.varchive.org/tac/twosre.htm
http://www.thebanmappingproject.com/sites/browse_tomb_831.html
http://www.thebanmappingproject.com/sites/browse_tomb_828.html
http://www.thebanmappingproject.com/sites/browse_tomb_861.html
http://www.thebanmappingproject.com/sites/browse_tomb_829.html