As I remember, the pharoahship descended through the woman, not the man.
That is the theory that has the most adherents among scholars at this time. The woman whose husband could be Pharaoh was called “the throne princess” or “the red princess.”
The book I noted above costs at least a hundred dollars now, but it must have been in a school or public library when I was a girl in the 1970s.
The pharaohs had to have been born from the same womb, figuratively at least -- so, there were arranged, consanguinous marriages, and dynasties coming to sudden ends for some odd reason. :^)
Hatshepsut, for example, was married to her own father, then her brother (or maybe half-brother), and finally her nephew, in succession. During her regency she wound up ruling in her own right for some period of years, while taking up with her companion Senenmut (there's actually an ancient contemporary graffito showing the two of them naked and doin' it, I think she's even shown wearing the crown), and bearing her daughter Neferure. Hatshepsut died, apparently, of a tooth abcess, and her successor was her nephew (obviously in some form or other they had a common female ancestor back along the line, or he had a female ancestor in common with her father and his own grandfather).
I believe the nephew was then married to Neferure, but she didn't survive long. Neferure's tomb was found by Howard Carter, but has AFAIK never been "cleared" or examined by Egyptologists (the interior was visited, so it can be seen in some form in one of those quickie crappy Zahi-approved documentaries). Despite its isolation and obscurity, the tomb was apparently looted and wrecked, as most were, in antiquity.
Akhenaten, whose name was wiped from every inscription after he died, was afterward referred to as "the criminal of Akhetaten" (his shortlived new capital) and appears to have been unable to keep it in his linen robes -- there's scene that survives that shows him making out with his own underage daughter while Nefertiti watches, and a second child looks at the mother and points at the action. It's also likely that he fathered at least one child by his own mother.
The 18th dynasty ended in a big mess, with Tut making nice with the Amun priesthood, but portrayed at least once trying to walk with a crutch. After Tut died young, his successor Ay (his uncle) is shown performing the rites of burial in person, very unusual -- and Tut was buried in a big fat hurry. It can't be proved to be connected, but Ay's sarcophagus was found smashed to pieces -- probably just a tomb robbery, but clearly there was a succession crisis, actually three or four in a row, right at the end of the 18th.