B2K singer De’Mario “Raz-B” Thornton and his wife, Mona Li Thornton, are mourning the death of their 3-month old son Astro. “It is with heavy hearts that we announce the unexpected passing of Astro Monte Thornton, beloved son of Mona and De’Mario ‘Raz B’ Thornton of the R&B supergroup B2K,” the couple’s spokesperson, David Robinson, told USA Today on Thursday, September 10. “The family asks for privacy as they navigate this difficult time. They truly appreciate your love and support.” No cause of death has been made public at this time. Us has reached out to Raz-B’s representatives for more information. Raz-B, 41, and Mona Li are also…