Sources close to the singer tell TMZ ... his ex, Ammika Harris, gave birth to their son. As we first reported in August ... it's their first child together.

Both Chris and Ammika shared cryptic messages on social media Thursday, seemingly announcing the birth of their baby boy. In fact, we know she did just that.

Chris posted a pic of himself smiling and looking down at something off camera with the caption of the date ... 11-20-19. Right after that, he shared a pic of himself wearing a hoodie with the word "BORN" embroidered on it.

Harris also alluded to the child's birth on her Instagram Story, writing ... "I was in love, when I first saw you."

The boy is Ammika's first child. CB has a 5-year-old daughter named Royalty with Nia Guzman.