A married Sydney couple have been jailed for "disturbing" sex crimes against their nine-year-old son.

The man, 57, and woman, 49, who cannot be named for legal reasons, had pleaded guilty to sexually assaulting the boy between January and November 2009 at their suburban Sydney home.

The father has also admitted streaming footage online of his wife and son engaging in sex acts.

At Sydney's Downing Centre District Court today, Judge Anthony Garling sentenced the man to serve a minimum of nine years' jail.

With time already served, he will be eligible for release in November 2018.