Pharaohs did publicly and with swag. It’s well-documented.
The other well-documented thing is Greek historians’ (specially Herodotus) hatred and false historiography of Persia.
That tradition still continues with movies like 300, that blatantly distort history.
Some things haven’t really changed![]()
Ptolemy was living in Hellenistic Egypt, and in this Egypt the practice of marrying siblings had spread amongst the noble non-royal classes. This is well documented.