Ancient Egyptian records point to degrees of acceptable incest.

For instance, religiously, sibling deities Shu and Tefnut married and had children, who also married each other. There is also evidence that incestuous relationships in Egyptian royalty also occurred during the Pharaonic period, though this appears to be confined to half-sibling relations. Incest amongst royalty however during this period is often contested due to the translation of texts at the time.

It was common to refer to your spouse as "my brother" or "my sister", regardless of blood relation and this has caused controversy. (Although this trend in speech might have been due to the commoners wanting to emulate their rulers.) The accepted reason for incest amongst the Pharaohs was to keep bloodlines pure, creating a sort of "dynastic cult" through this.