The remains of Tutankamun’s Parents, Akhenaten and the mummy only identified as “The Younger Lady”, and his grandparents, Queen Tiye and Amenhotep III. It was recently proved this “Younger Lady” mummy is in fact Tutankamun’s mother, and a full sister to Akhenaten. Thus King Tut only had one set of grandparents.
BIOLOGICAL MOTHER OF KING TUT, is the mummy called "The Younger Lady" of KV35.
Not long ago it was the norm in America (and still is in a good part of the world) to be having sex (and having children) at sixteen years old. Our grandparents (or great-grandparents for the younger ladies) were married with several children by the time they were 19-20. And so it has been since the dawn of time up until about 50 years ago.
French Egyptologist Asserts that the Younger Lady is Really the Mummy of Nefertiti http://www.ancient-origins.net/news-history-archaeology/french-egyptologist-asserts-younger-lady-really-mummy-nefertiti-004683