Son, 46, arrested after parents found dead

A 46-year-old man has been arrested after the bodies of his elderly parents were found in the southern Sydney home they all shared.

Police say the bodies were discovered at the Sutherland home shortly after 8am on Tuesday following a "concern for welfare" report.

"The deceased are believed to be the man's 71-year-old mother and 75-year-old father," NSW Police said in a statement.

Both had sustained a number of injuries.

The son, who was arrested at the house, is now under police guard in hospital where he's being treated for non-life-threatening injuries.

Detective Superintendent Jason Box says he's made "certain comments" and "admissions".

It's expected he'll be charged later on Tuesday.

A crime scene has been established at the Tudar Road house which is being examined by forensic officers. The bodies were found in a bedroom and the lounge room.

The couple's other middle-aged son has been informed his parents are dead and his brother has been arrested, Det Supt Box told reporters.

"(Officers) have done a fantastic job given the reasonably traumatic scenes they've come across," he added.

"It's quite confronting."