There seems to be an unwritten law that presidential siblings are supposed to be a bit embarrassing. But in that crowded field one name really stands out in my memory.
When he wasn't accepting money from Libya, Billy Carter, brother of President Jimmy Carter, took his name to market in the form of "Billy Beer" in the 1970s.
But his real crime was allowing his name to be on the worst beer it was ever my displeasure to consume. I think they let this stuff age about 15 minutes before sending it out on the market.
