Between Akhenaten and Tutankhamun, Manetho mentions two sovereigns named “Akhenkherres”, a man and a woman; the latter is referred to as “king’s daughter”. This situation is reflected in Egyptian sources (inscriptions on blocks and stelae, seal impressions, “labels” of jars) which mention two rulers in the Amarnian age with a praenomen (ie name of throne) similar to Akhenkherres: Ankhkheprure and Ankhetkheprure. The second form is distinguished from the first by the presence of the feminine marker -et-; this element, combined with the Manetonian tradition, a series of archaeological evidences and the presence of some female epithets, suggests that Ankhetkheprure was a woman.
Today the most accredited hypothesis is that Ankhkheprure and Ankhetkheprure should be identified with Smenkhkare and his wife Meritaton. The attestations of an Ankhetkheprure ruler would indicate that for a time Meritaton also ruled as pharaoh; however, there is no agreement on the location of his kingdom, which could have preceded or followed that of his consort Smenkhkare. The situation is complicated by the fact that both throne names, Ankhkheprure and Ankhetkheprure, are found associated with the birth name Nefernefruaten. Since Nefernefruaten is also attested as the name of Aton of Nefertiti, it has been assumed that Ankhetkheprure Nefernefruaten was actually the same Nefertiti, associated with power by Akhenaten and surviving him. In this case, the reign of female pharaoh Ankhetkheprure should be placed between the death of Akhenaten and the enthronement of Smenkhkare. However, if you believe the Manetonian tradition according to which “Akhenkherres” was the daughter of a king, Meritaton seems to be preferred to Nefertiti as a candidate for identification with Ankhetkheprure Nefernefruaten, also because it is not sure that Nefertiti survived Akhenaten.
According to some scholars, both the names Ankhkheprure Nefernefruaten and Ankhetkheprure Nefernefruaten refer to Meritaton. However, recently some archaeological evidence that seems to disprove this hypothesis: in particular, some stelae in which Ankhkheprure-Nefernefruaten has male physical characteristics and, above all, is accompanied by his wife. Furthermore, Meritaten is attested on a cassette from Tutankhamun’s tomb as the great royal wife of Ankhkheprure Nefernefruaten. It is therefore speculated that Ankhkheprure Smenkhkare at some point in his reign changed his name to Ankhkheprure Nefernefruaten; the new name would have been chosen in homage to Nefertiti, or in any case to establish a sort of dynastic link.
The succession of names Smenkhkare> Nefernefruaten may be a clue that Meritaten, like pharaoh Ankhetkheprure Nefernefruaten, occupied the throne after Smenkhkare’s death and took his names. Another clue to this is that the Ankhetkheprure form comes as a feminine variant derived from the name Ankhkheprure. The epithet “useful to his consort” which is attributed to Ankhetkheprure Nefernefruaten would therefore refer to Smenkhkare; if instead the reign of Meritaten directly followed that of Akhenaten, it is to the latter that the epithet would refer, since Meritaten is attested as Akhenaten’s wife in the last years of his reign.
The first hypothesis, that which sees the succession Akhenaten, Smenkhkare, Meritaten as pharaoh, seems to be preferred anyway. It remains difficult to determine how long Smenkhkare and Ankhetkheprure (aka Meritaten) reigned; in case Meritaten calculated his years of reign independently from the spouse, we would have 3 years for Smenkhkare and one for Meritaten; however, it is also possible that the latter continued to count the years of her late husband and in this case her first year of reign could coincide with the second or third of Smenkhkare.