Original: In 2009 the unofficial biography There Will Be Rainbows : A Biography of Rufus Wainwright and the story of Loudon Wainwright and Kate McGarrigle by Kirk Lake documented Wainwright 's early struggles .
Simplified: He is the son of singers and performers Loudon Wainwright III and Kate McGarrigle . His sister Martha Wainwright is also a well known singer .