I would really like to see the autosomal DNA of King Thutmose IV so that a question could perhaps be answered once and for all: Did the pharaohs of Egypt kill their brothers like the sultans of Turkey did for a time once they had produced their first male heir? This was done in order to avoid possible civil war and intrigues. It was a cruel practice but there are indications it may have been followed in ancient Egypt. No man is ever styled “king's brother”, although “king's sister” is attested. King Ramesses II constructed a huge tomb, KV5, evidently meant for his children. Did he do this because so many had already predeceased him [and he had very many children]—or in anticipation of a dreaded day? Egyptian texts are silent on the subject. On the other hand, a son of the one-time heir of Ramesses the Great, Khaemwaset, did live to have an illustrious career. But he was the nephew and not the brother of Merneptah, the king's son who managed to succeed his father. Perhaps a nephew's claim to the throne was thought negligible by the the polygamous pharaohs, who anticipated having numerous offspring of their own.
Since the autosomal results for Tutankhamun and some of his family members were released, it has been noticed that Yuya, an ancestor of the young king, shared significant alleles with Tutankhamun's grandfather, Amenhotep III. However, without seeing the DNA of the father of the latter, we cannot know if Yuya was related to Amenhotep III on his father's side or his mother's. If Yuya shared alleles with Thutmose IV, he may have been his brother [or even his paternal uncle, depending upon the age of Yuya] which would mean it was possible for the brothers of kings to survive and even become important men. If they were not styled “king's brother”, it may have been for some other reason having merely to do with protocol.
This is something that requires more investigation, but first we need to isolate the y-DNA of the pharaohs of the dynasties and create a database with which the y-DNA of other male mummies could be compared. If this DNA could be discovered in the general population, then that would prove that royal fratricide was not a common practice in the Egypt of the pharaohs. On a positive note, KV5 apparently never saw the burials for which it was constructed. But, if any other Egyptian monarch may be suspected of having numerous children—and sons—it would be Amenhotep III. And, yet, according to a royal lady of the post-Amarna period in a letter to the King of the Hittites, there was no one left for her to marry but a servant. If the writer was Ankhesenamun and she was telling the truth, then perhaps even her elder sister, Meritaten, had to marry a “servant” there at Akhetaten, who became the short-lived King Smenkhkare by virtue of this union, and Ankhesenamun did not want to do the same. On the other hand, it is rumored that DNA close to that of Tutankhamun has been discovered in a modern Druse population. If true, that would not have come via Tutankhamun, who evidently was the end of his line, but some predecessor.