Ptolemy XIII was Pharaoh of Egypt from 51 to 47 BC (remember we’re counting backwards here), his reign pretty much demonstrating the bad luck associated with the number thirteen (in fact he could have been nicknamed Ptolemy the Unlucky or Friday the XIII).
Ptolemy XIII succeeded his father Ptolemy XII, becoming co-ruler by marrying Cleopatra who was his older sister at the time. She was Cleopatra VII, but she was the Cleopatra we all know about — the one of Antony and Caesar and the asp and all that. Since XIII was only 11 at the time, he had a regent — and should you be thinking about the regent’s duties vis-à-vis Cleopatra, we’ll point out that the regent’s name was Pothinus the Eunuch.
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Cleopatra, it turns out, was a bit of a grandstander, strutting about as Queen, putting her image on coins, and generally hogging the Egyptian spotlight. Thus in 48 BC, XIII and his eunuch tried to depose her, but she ran off to Syria and raised herself an army.
Enter Roman general Pompey, seeking sanctuary from Julius Caesar. XIII pretended to welcome Pompey but had him murdered instead. When Caesar arrived, XIII gave him Pompey’s head as a little welcoming gift. Caesar was unimpressed and took Cleopatra as his welcoming gift instead, giving XIII a cold Roman shoulder and killing his eunuch for good measure.
While Caesar and Cleopatra kept busy trysting the night away, XIII in cahoots with another sister (it’s great to be able to toss in another sibling when things are beginning to slow down) tried again to dump Cleopatra.
XIII and his other sister were no match for Caesar and Cleopatra and in the ensuing Battle of the Nile, XIII was forced to flee. Unfortunately, Ptolemy the Unlucky was drowned as he attempted to cross the Nile.
Wretched Richard's Almanac 
Thanks for simplification of this complex story. When DJT declares himself Caesar, heads will once again roll. And I’ll be an ex-pat.
Perhaps we should get his eunuch if we can figure out who it is. We have a whole Houseful to choose from.