Singer and pop peculiarity Michael Jackson has quietly added a baby boy to his brood, PEOPLE reports in its latest issue. The singer brought the 6-month-old baby backstage at Siegfried and Roy's Las Vegas show on July 30, along with his other two children, Prince Michael, 5, and daughter Paris, 4. "The baby was a surprise," a source told PEOPLE. "(Jackson) said, 'This is my third child.'" Equally surprising is the baby's name. PEOPLE has learned that Jackson has been introducing the tot as "Prince Michael II," or simply "No. 3." The identity of the child's mother (sources tell PEOPLE that the child was not adopted and was conceived "the natural way") remains another mystery. Friends say Jackson's ex-wife Deborah Rowe, 43, a former dermatologist's assistant and the mother of Jackson's older children, is a distinct possibility, according to PEOPLE. Rowe was divorced from Jackson in 1999 after three years of marriage. The new baby comes at a professionally difficult time for Jackson, who turns 44 on August 29. His most recent album "Invincible," released last November on Sony Music's Epic label, sold just 2 million copies in the U.S. and fared poorly overseas. Earlier this summer, Jackson waged a war against Sony, blaming the album's performance on the label and its chief, Tommy Mottola. However difficult his recent business dealings, sources tell PEOPLE that the pop star, who recently made a self-deprecating cameo appearance in "Men In Black II," is very happy with his growing family. Jackson "is extremely impressive as a father," producer Gary Pudney tells PEOPLE. "He had a very lonely childhood. His motivation in having children is partly because of that but mainly because he loves them."