(FORTUNE Magazine) – We'll begin to answer this question of blood ties between the Oracle of Omaha and the Minstrel of Margaritaville by pointing out their similarities, which are haunting. Both play stringed instruments: Jimmy a tropical guitar, Warren a mean ukulele. ("I've probably had worse musicians in my band," jokes Jimmy.) They've both cashed in on unlikely investments: Warren bet on furniture, insurance, and vacuum cleaners and is now worth $35 billion; Jimmy bet on the illusion of a colada-drenched beach bum and forged a multi-million-dollar brand with over 30 albums, eight movies, a clothing line, nightclubs, a custom record label, three best-selling novels, and hundreds of gift-shop gimmicks. Jimmy's a Capricorn, adept at accumulating money; Warren's a Virgo, with a creative musical mind.

Both keep it real by sticking to what they know: Warren by avoiding tech stocks, Jimmy by milking a song he recorded more than a generation ago. Both attract cult followings: Parrotheads flock to Jimmy's summer concerts; investors flock to Warren's Berkshire Hathaway shareholder meetings--Warren himself calls it the capitalists' Woodstock. Both avoid changes in latitudes and changes in attitudes: Warren's a diehard Husker; Jimmy's still wasting away in mythical Margaritaville. ("Lethargy bordering on sloth" is how Buffett describes the cornerstone of his style. That's Warren on investing, not Jimmy on chilling.) And in his classic "Cheeseburger in Paradise," Jimmy croons, "Heaven on earth with an onion slice." Hamburgers are Warren's favorite food.

But really: Are they related? FORTUNE believes, but cannot prove beyond a doubt, that Warren and Jimmy are kin. It was Warren's sister Doris, the family genealogist, who first raised the subject. Two years after mailing out questionnaires to all 125 Buffetts in the U.S., she got a call from a curious Jimmy. "He said, 'I want to be related to your family because they're rich and famous,' " Doris recalls. "And I said, 'That's funny, we want to be related to you because you're rich and famous.' " Doris' research has unearthed three possible ancestral links: John Buffett, a poor 17th-century pickle farmer from Long Island; a Newfoundland sailor whom Jimmy honors in "Son of a Son of a Sailor"; and Norfolk Island in the South Pacific, which is inhabited by hundreds of Buffetts (as well as a good many descendants of the mutineers of the Bounty). When Doris and Jimmy discovered that Norfolk Island used to be a penal colony, however, they lost hope: Centuries of inbreeding have blurred family lines.

Despite the lack of absolute proof that they're related (as of press time, no DNA testing had been conducted), Warren and Jimmy have become friends. While Jimmy insists "Uncle Warren" doesn't slip him any investing tips, the two have been known to break out in song. "I think he's angling to get into my will," the billionaire Buffett jokes. "But the way things are going, I'd rather be in his."

--Tyler Maroney