Why are the Ptolemaioi such a hated faction?

[Raygereio]

Wel, at least their family tree is one of the clearest ones I've ever seen.
And don't you just hate when you have to scroll horizontally? No such thing necessary here.

Forgive me if I am wrong, but I thought Caesar's child with Cleopatra the Slut was named Caesarion not Ptolemy XV.

My encyclopedia says: Ptolemy XV Caesar.
Full name Ptolemy Philopator Philometor Caesar.
Nicknamed: Caesarion.