*rolls up late to the party and wheels out soap box*
You know who did practice incest almost exclusively but cops zero shit for it in the public consciousness? The Ptolemies. There's so many of them and almost all of them did it. The Old Kingdom was doing it more than say your average New Kingdom pharaoh but no one was doing it like the Ptolemies
Even if Tutankhamun's parents were closely related such as *spins wheel* full siblings *throws dart* cousins, Amenhotep and Tiye were sooooo unrelated. Tiyes dad Yuya is some random minor nobleman and they are from Akhmim of all places. (We have the most attestations of them from their burial which calls them iry-pat hereditary noble among other things which is a rank you can just be elevated to btw despite what the translation implies ergo at their highest status at the end of their lives because their daughter is the king's chief wife and has been for some time). Some researchers try to suggest weeeeelll maybe Yuyas sister was Amenhotep's mother Mutemwiya to try and explain how they were connected to the royal family but literally we do not know we have no filiation for any of these people we do not know who their parents are so how can we know if they are related! Amenhotep III was the son of a minor wife who we know nothing about because she wasn't important and we only know about her because her son became king and elevated her status and erected statues of her and included her on his
You get actual confirmed incest marriages every generation or so but in the 18th Dynasty they rarely result in the heir who inherits the throne. For example, Amenhotep III's dad, Thutmose IV married his sister Iaret (full or half is unknown, we don't know who her mother is). She may be the mother of some of his attested children but their mothers are not specified in the surviving inscriptions so, dunno
Thutmose IV's dad Amenhotep II just, refused to name any of his wives on monuments (presumably nuked in response to the threat any royal women might conceivably pose a la Hatshepsut), so his only know wife is Tiaa, mother of TIV and a minor wife, unrelated, before her son elevated her to chief wife status when he took the throne
Amenhotep II's dad Thutmose III didn't marry a sister as far as we can tell. He was also a son of Iset, an unrelated minor wife of his father, Thutmose II. It's sometimes suggested he married his half sister/cousin Neferure to explain the parentage of a prince called Amenemhat but she's never called Kings Wife anywhere so, dubious. Neferure WAS a product of incest, her parents being half-siblings. Her father Thutmose II was a half brother by, you guessed it, a minor wife, Mutneferet, and her mother Hatshepsut was herself a child of Thutmose I by his chief wife Ahmose
Now, here, finally, with Thutmose II, we hit some incest that results in the heir to the throne. Thutmose II's mother was Mutneferet, a minor wife, possibly a cousin of her husband Thutmose I (we're unsure exactly who her dad is, maybe Ahmose I. She's a Kings Mother, Kings Wife, Kings Sister, Kings Daughter). Ahmose, mother of Hatshepsut, was probably Thutmose I's sister.
Going back beyond this to the first couple of kings of the 18th Dynasty is more incesty, as are the last few of the 17th Dynasty. Maybe 3 generations of brother-sister marriage going on but that's the longest span you get for the entire 18th Dynasty. Thutmose I's parents are siblings, and maaaaybe Amenhotep I's are cousins but he comes kind of out of nowhere and doesn't leave a male heir. Seqenenre Tao married his sister, but his parents Tao I and Tetisheri are unrelated
So like, if Inbreeding For One (1) Generation Made Tutankhamun Die Young, uhhhh why don't we think that about the early Thutmosids who by all accounts Did Shit and Lived A Bit Longer. Caveat, Thutmose II died kind of young, but it's Ancient Egypt anything could be fatal, kings aren't immune. Thutmose IV died youngish too but it's not The Incest