On a cul-de-sac in a leafy residential subdivision in this booming oil town 30 miles west of Houston, Andrew and Aaron Harrison were raised to look out for each other, as perhaps only identical twins could. They shared a room in a six-bedroom house, though they had no other siblings. When each grew to stand 6 feet 6 inches, their father, Aaron Harrison Sr., encouraged them to switch rooms, and only then did they relent. They moved their beds into the family room and occupied that. They rollerbladed and took piano lessons together and, of course, played basketball, beginning at age 3, on the sidelines of their father’s Y.M.C.A. pickup games and rolling onward, until they could dunk at age 11, and college recruitment letters — as many as 30 a day — began flooding the Harrisons’ mailbox. The twins chose Kentucky, and after a fitful few months this season, they have returned to Texas for the Final Four as the Wildcats’ starting backcourt, playing perhaps as well as they ever have. If, as many project, the twins head directly to the N.B.A. after the season, it will not surprise those who prophesied as much when the Harrisons were in middle school.