This sounds like Brain Child by George Turner. It was published in 1991 so you could have read it ten years ago.
Young journalist David Chance, who had thought himself an orphan, receives a message from his real father, Arthur Hazard, urging David to join him in exploring the unpublicized and unplumbed aspects of the intelligence-enhancing project that produced Arthur and others but eventually ended in disaster. Three groups of children were created; the first (Arthur's group) became technological whizzes; the second, gifted artists; the third developed intelligence so exceptional as to be incomprehensible, even to the other two groups, and eventually killed themselves. The third group's leader, Conrad, left a mysterious ``legacy'' that previous investigations have failed to discover. Where, and what, might this legacy be? First, Arthur sends David to tackle Armstrong, the still powerful and dangerous politician who originated the project. Soon, government security agents take note of David's activities. The legacy, it emerges, is a technique for achieving immortality. But who could be trusted with such a secret?
The young feller is Conrad (I don't think he has a surname). Conrad is one of the Group C mutants who are so far ahead of normal humans that they can manipulate them as pets.
The art collector is one of the Group B mutants who were designed to have superior emotional powers. She possess paintings that when looked at manipulate human minds.
David's father is one of the Group A mutants who were designed to be superior technologists.
Conrad (Young Feller) committed suicide and left a cryptic message saying he had discovered something that would transform the human race, and David's father wants David to try and discover this secret.
At the end of the novel legacy is revealed as:
“As for Mr. Armstrong’s carrot, immortality, it is a donkey’s meal. In a system that depends on death and birth for its operation, immortality is nonsense. Conrad’s theorems confirm it. A vastly extended life span is attainable—and that is Conrad’s murderous joke, his farewell to the donkeys who would eventually decipher it and take the idiot risk of reaching for the carrot. He built a very human nastiness into the last panel; perhaps your treatment of him shattered all pity. The panel stressed the simplicity of manipulation but most subtly hid the cost. We found it because we suspected something of the kind, but we had to peer closely. Conrad thought that a transparent greed for life, like Mr. Armstrong’s, would reach for it without caring for anything but the splendid, blinding fact.
“The methods vary. In most of them the price is sterility or teratological deformity. In some, prenatal cancer is inbuilt, basic to the helix and ineradicable. At this stage in man’s career longevity—save by such regular medical props as presently preserve your Honoured few like pickles in a jar—is only a useless flourish. Conrad’s legacy was at best a mockery, at worst a deranged joke. He surely did not foresee that it would be preserved as a holy relic by Belinda whom he depended on to exhibit it. The joke has been on Conrad and now it is over. Laugh if you can.”