$sql = $DB_con->query("
SELECT cedula, nombresyapellidos, edad
FROM (SELECT cedula,nombresyapellidos, MAX(edad) edad FROM estudiantes) estudiantes WHERE cedula=:cedula;");
$consulta = $DB_con->prepare($sql);
$consulta->execute(array(':cedula'=>$cedula));
if($consulta->rowCount() > 0){