Julia Roberts' beloved mother has died aged 80.

The 47-year-old actress has been left heartbroken after Betty Lou Bredemus passed away this morning (19.02.15) after losing her battle with lung cancer, according to PEOPLE.com.

Betty had been living with Julia, her husband Daniel Moder and their three children at her Los Angeles home but it is thought she died at St John's Health Center in Santa Monica, California.

It is believed Betty had been suffering with the disease for some time following reports a cancerous tumour was discovered on her lung during a routine MRI scan in November 2013.

The death of Betty Lou comes just 12 months after her daughter Nancy Motes - Julia's half-sister - died from an drugs overdose.

The shocking death was declared as suicide last May following various toxicology tests and an autopsy.

Officials revealed at the time that Nancy, 37, was discovered drowned in her bath on February 9, 2014, after taking various substances. Her body was also found with a note.

The 'August: Osage County' star admitted previously that her sibling's sudden death had hit her and their family hard.

She said: ''It's just heartbreak ... You don't want anything bad to happen to anyone, but there are so many tragic, painful, inexplicable things in the world. But [as with] any situation of challenge and despair, we must find a way, as a family. It's so hard to formulate a sentence about it outside the weepy huddle of my family. ... Meditation or chanting or any of those things can be so joyous and also very quieting.''