Portentous petraportals - Interlude (curse of the mummy)
In short, Isis and Osiris (brother/sister, husband/wife) were appointed rulers of Egypt by their parents Nut and Geb. Set (brother to Isis and Osiris) tricked his way onto the throne and killed Osiris. Isis went looking for him, resurrected him, had a child with him (Horus) and eventually Isis and Horus overthrew Set and drove him into the Red Sea.
Set’s sister/wife Nephthys had a son (Anubis) with Osiris before he was killed. Isis raised him too.
The Sect of Setesh had a slightly different take on matters.