There is the old debate about who borrowed from whom, i.e. Liszt from Wagner or Wagner from Liszt. Liszt eventually became Wagner's father-in-law after Liszt's daughter Cosima left her imperious but talented musician-husband, Hans von Bulow. Von Bulow was once a student of Liszt.
http://www.soundsandfury.com/soundsandfury/2004/07/detective_story.html