Historical clue formulations

• A Marx brother — 2016-10-12
• One of Groucho's brothers — 2016-05-24
• Youngest of five famous brothers — 2013-03-02
• One of the Marx Brothers — 2012-06-17
• Herbert Marx, familiarly — 2004-12-19
• A Marx brother — 2001-01-12
• Marx-man — 1994-01-15