The Queen Mother was higher in rank than the wife of the king. She was sometimes portrayed beside her son on the throne instead of Maat, goddess of justice.
The chief, or primary, wives of kings were mostly chosen from the royal family so that the royal blood would be continued. This also served to legitimize the accession to the throne for the sons as being offspring of divine origin.
Some kings married daughters of high officials of non-royal blood to strengthen ties with these officials. Other kings married foreign princesses as a kind of friendly diplomacy between Egypt and the foreign country.
Tuthmosis the Third married three Asiatic princesses and Tuthmosis the Fourth married a Mitannian princess, as did his son Amenhotep the Third.
An Asiatic queen of Ramesses the Second held the position of the "Great Royal Wife". Another Asiatic queen was the mother of King Siptah of the Nineteenth Dynasty and the mother-in-law of Ramesses the Third also came from Asia.
Some kings married their own daughters. Amenhotep the Third married his daughter Sitamun and Akhenaten married two of his daughters, Meritaten and Ankhesenpaaten.
When Akhenaten was presumably married to Kiya, mother of Tutankhamun, she was given the position of the "Wife and Great Beloved One" and not a "King's Wife".
Ramesses the Second also married two daughters, Meritamun and Bentanta.
It seems that such marriages were not real, but sort of honorary marriages. By this act, these princesses were allowed to accompany their fathers in official appearances and obligations.