Did Cleopatra Do Incest?

It was custom in Egypt to marry a sibling. So incest was custom to protect the royal line. The amount of murderiness that Cleopatra did was probably slightly above the baseline level, but it was still OK. She knew by bumping off siblings that she would be able to consolidate her power more. Is this a classic case of this was the done thing at the time? That's my feeling. Oldie-worldy times, different rules. It well, and let's not forget poor old arson the way as well. Didn't end too well.