The racing debut of Roy and Gretchen Jackson's 3-year-old colt Nicanor on Saturday at Gulfstream Park is easily the most anticipated arrival of a full brother since Zeppo Marx replaced Gummo in the family's vaudeville act 91 years ago.\nAt least, this is what an unsuspecting sports world is being led to believe, as if the next savior has arrived, and hearts will once again soar. The public relations pressure being put on this innocent colt to make the same kind of headlines as brother Barbaro is both misplaced and mildly amusing. Someone forgot to crack the history books.\nAnd other sources as well. In all discussions pertaining to the repetition of transcendent quality in full Thoroughbred siblings, I always turn to the wisdom of Ron McAnally's former barn foreman, the late Aureliano "Cuba" Baez, who played professional baseball and jai alai and could flip quarters like nobody's business. His nickname was pronounced "kooba."\nWhen informed that a new horse in the barn was a full brother to an accomplished stakes winner, Cuba snorted.\n"I got a dozen full brothers back in Havana," he said. "Not one of them is worth a damn."\nThus endeth the lesson.\nNicanor could turn out to be a decent colt, perhaps even a stakes winner, which would be great. The game could use the positive vibe. But for Nicanor to become another Barbaro - the unbeaten Kentucky Derby-winning Barbaro, not the martyred Barbaro - he would need to rise to a very high bar of full-brother achievement. We're not talking Billy and Jimmy Carter here. More like the Baldwins.\nThe fact that identical matings produced wildly different results flies rudely in the face of the idea that Thoroughbred breeding is a selected, quasi-scientific process. After all, thousands of hours and consultancy dollars are spent on mixing and matching sires and dams. Why wouldn't what's worked before automatically work again, especially in the best of the breed?\n"I don't think there's any magic to it," said Mack Miller, who trained Kentucky Derby winner Sea Hero and bred Kentucky Oaks winner Lite Light. "That's just the luck of the game. Sometimes, you just experiment. Sea Hero's dam threw nothing but good horses, but it was amazing he could even run. He was by a well-bred but very ordinary sire" - Polish Navy - "a real one-shot thing, and they never sent the mare back to him."\nThere was only one Man o' War, but it wasn't for lack of trying. Big Red had two full brothers and two full sisters, but the only one of consequence was My Play, winner of the Jockey Club Gold Cup - just like his older brother.\nThe Haste mare Quickly had five foals, four by the stallion Reigh Count. One of them was Count Fleet, the others were not.\nAlfred Vanderbilt tried five times to replicate Native Dancer through full brothers and sisters. Two were unraced and the other three won 2 of 48 starts.\nBold Ruler, the 1957 Horse of the Year, had an older full brother named Independence who went into another line of work and ended up winning the 1961 American Grand National Steeplechase. Their full brother and three full sisters did considerably less.\nSo it goes, down through the ages. Secretariat, Bold Ruler's most famous son, already had two older full sisters in the mix by the time he came along. Neither one stopped the presses.\nAffirmed had a full sister who never raced and a full brother, named Silent Fox, who tried hard but could only manage to finish third in the Charles H. Strub Stakes. Five years earlier, Affirmed won the same event by 10 lengths, along with a second title as Horse of the Year.\nIron Reward was a remarkable mare. Next month, she is being inducted into the California Thoroughbred Breeders' Association Hall of Fame. Of her 11 foals, eight were by Khaled, including stakes winners Like Magic and The Shoe, stakes-placed Molly Maid, and the 1956 Horse of the Year, Swaps. Close, but no cigar.\nCigar had no full sisters or full brothers. Neither did Kelso, Buckpasser, Seattle Slew, Spectacular Bid, John Henry, Ack Ack, Genuine Risk, or Ruffian. Why try? Nashua had one full sister, named Stavroula, who never raced. Damascus had one lonely full brother who didn't even get a name and a full sister who won four times. Her name was Arlene Francis.\nRound Table had one full sister, named Monarchy, who won the Arlington-Washington Lassie. Foredate, Forego's full sister, never started. Dr. Fager's lone full brother was Highlander, who hit the board in races like the Vosburgh and the Withers and won 9 of 29, but could never begin to follow in the good doctor's footsteps.\n"He could run a little, but of course he was a disappointment to us," said John Nerud, who bred and trained them both for William McKnight. "He didn't have the spark like his brother.\n"It seldom happens, though," Nerud added. "The greatest trainer of all, who taught me how to train horses, was Ben Jones. People would come up to him and say, 'This is a full brother to so-and-so.' He'd say, 'John L. Sullivan's mother had seven sons, and only one John L.' "\nSounds familiar. And for the record, Citation, the best Ben Jones ever trained, had a full sister and a full brother who never raced, while another full brother won 3 of 9 starts. His name was Unbelievable.