I've recently read up on my Rameses history. It seems that a few amount of Iset-Nofret's children survived, but I think maybe only one of Nefertari's survived.

List-

Sons-

Amun-her-khepseshef-some say he died in year 40-45
Pa-Re-her-wenemef-who they say died early, in year 30.
Mery-Re I-died young
Meriatum- who it looks as if Ramses passed over for crown prince. Could it be he had his own life and family and didn't want to become king? (pure guess work mind you)
Montu-her-khepeshef-would seem like a canidate for Nefertari and Rameses, mainly because of the similarity in names as the first two.
Ptah-her-khepeshef-Is he the first born just with a different name?
Daughters-
Merit-Amun-Died during her fathers reign.
nefertari II-Died young.
Henuttawy-?
Nebettawy-?
Beketmut-??

Though they say Nefertari could have had up to 9 or more children by rameses. Which would leave 3 (unless we count Montu-her-khepeshef which would leave us with atleast one more child) and with
Amun-her-khepseshef being crown prince until his death, it would seem by that time he would have acquired a wife, and children, yett there's no mention of it.