"The one with the power to vanquish the Dark Lord approaches ... born to those who have thrice defied him, born as the seventh month dies ... and the Dark Lord will mark them as his equal, but they will have power the Dark Lord knows not ... and either must die at the hand of the other for neither can live while the other survives ... the one with the power to vanquish the Dark Lord will be born as the seventh month dies ..."
Dumbledore thought about the prophecy and knew that both the Potters and the Longbottoms were due to give birth at the end of July, he knew that the Dark Lord Voldemort would go after the Potters given that their secret keeper was Peter Pettigrew, one of Tom's own followers. He also knew that Severus had been outside when Sybil had foretold their future, the foolish lonesome boy would no doubt go running to his Master in an attempt to gain some acknowledgement.
He found it sad that both the Potters and the Longbottoms would have to suffer, but he needed to know which boy to train which boy to coddle, and which boy to manipulate for his plan to work, after all he didn't spend all that time making Tom Riddle what he was for it to all go wrong because one stupid woman couldn't be precise.
Yes he would groom the boy into the perfect weapon, and then have him kill the boy, and in time he would kill the boy becoming the most powerful wizard alive again. He had loathed the fact that a filthy little half-breed like tom had had more power. That was why he had driven him to the dark side buy making sure his childhood was a horrid as it could have been.
He Albus Dumbledore was the greatest wizard alive and only his children would be more powerful than him, anyone else who dared to have more power than him would Perish.