Sad news out of Montreal: Folk singer Kate McGarrigle -- the former wife of Loudon Wainright III, and mother to Rufus and Martha Wainwright -- died of liver cancer today. She was 63. Here's footage from last December, of Kate with children Rufus and Martha Wainwright performing the English Christmas song, "In the Bleak Midwinter." Just gorgeous. Have a Kleenex handy. After the jump, footage of Rufus playing "Beauty Mark," which he wrote for his mom.