Washington - Egyptologists researching a mummy first discovered in 1898 believe it is the mummy of Queen Nefertiti, a legendary beauty and wife of the renegade pharaoh Akhenaten, the Discovery Channel said on Monday. Virtually all traces of Nefertiti and her "heretic" husband, who ruled from 1353-1336 BC, were erased after his unsuccessful attempt to overthrow the pantheon of the gods to worship the sun god Aton - among the earliest known practices of monotheism. Nefertiti also was stepmother of the boy-king Tutankhamen, whose tomb was discovered in 1922.
Akhenaten was the husband of Nefertiti but was not the step-mother of Tutankhamen. 
Nefertiti was the stop-mother of King-Tut, not Akhenaten. I think that there might have been too many conditions for the system to check and the system was probably fooled by the gender specific wording (step-mother). 
( z1 contrast :ARG1 ( z2 have-rel-role :ARG0 ( z3 person :name ( z4 name :op "Akhenaten" ) ) :ARG1 ( z5 person :name ( z6 name :op "Nefertiti" ) ) :ARG2 ( z7 husband ) ) :ARG2 ( z8 stepmother :polarity - :ARG0 z3 :ARG1 ( z9 person :name ( z10 name :op "Tutankhamen" ) ) ) )