Noted Canadian singer-songwriter Kate McGarrigle, mother of vocalists Rufus and Martha Wainwright, died Monday in Montreal. She was 63.

McGarrigle had battled cancer since 2006. Her condition worsened over the weekend, and CBC News reported that Rufus Wainwright had cancelled a tour of Australia and New Zealand to be with her.

As the McGarrigle Sisters, Kate and elder sibling Anna attracted critical attention in the ’70s with their intimate folk-inflected harmony singing and poignant, sometimes drolly observant writing.

Born in St. Sauveur-de-Monts, Quebec, in 1946, Kate McGarrigle sang with her sister in the folk group the Mountain City Four in Montreal during the early 60s. Working as a duo, the sisters supplied music for the Oscar-nominated doc “Helicopter Canada” in 1966.

The act split up for a time in the early 70s, when Kate worked in the New York folk clubs and married singer-songwriter Loudon Wainwright III (whom she later divorced following the birth of their two children).

The sisters regrouped in 1974, around the time that Linda Ronstadt scored a breakthrough solo hit with “Heart Like a Wheel,” penned by Anna. The McGarrigles’ material would later be covered by Maria Muldaur, Judy Collins, Billy Bragg and the trio of Ronstadt, Dolly Parton and Emmylou Harris.

The McGarrigle Sisters were signed to Warner Bros. Records in 1976; their well-received debut album was produced by Joe Boyd. While they never attained similar acclaim or commercial success, the McGarrigles boasted a devoted following and recorded nine more albums for such labels as Kebec Disc (for which they performed in French), Polydor, Private Music and Boyd’s imprint Hannibal. Their last release was a 2005 Christmas album.

In 1993 the McGarrigle Sisters were honored with the Order of Canada for their contributions to the nation’s music.