In Egyptian mythology, Osiris was Anubis’s father in the best-known Osiris family genealogy.
This genealogy identifies Anubis as the son of Osiris and Nephthys. In the myth, Nephthys is said to have concealed her identity from Seth and taken the form of Isis when she conceived Anubis with Osiris. Isis later found and protected the infant Anubis in some versions of the story.
Osiris was the god who became ruler of the dead after Seth murdered and dismembered him. The relationship between Osiris and Anubis therefore connects two major parts of Egyptian funerary religion: Anubis’s work in embalming and guiding the dead, and Osiris’s authority as the ruler of the afterlife.
Egyptian mythology preserves multiple traditions, and Anubis’s parentage was not identical in every period or source. The Osiris genealogy is the familiar family arrangement in later mythological summaries and is the answer intended by this question.