Jean John Silah was supposed to return Greg to his mother on July 2, but he failed to do so.
In the past, Silah has threatened to take their son to his home country of Syria.
Jean John's brother, George Silah, 46, also had his sons, Alexander Silah, 12, and Zaven Silah, 8, for a visit at their home in the 7300 block of West 81st St. in Los Angeles. The brothers lived together at this residence.
George Silah was scheduled to take a cruise with his sons on July 5, but never boarded the cruise.
The children's mother has not had any contact with her children since.
Investigators discovered that the brothers have not paid their rent for several months and their residence appears to have been abandoned.
Anyone with any information regarding this case is asked to Pacific Area Detectives at (310) 482-6313. After hours and on the weekends, please call 1-877-LAWFULL.