Stern said they are confident he is the father and "based on when the timing of when the baby was born, there really is no doubt in either of our minds."
Entertainment reporter and photographer Larry Birkhead claims he has proof Danilynne Hope is his daughter and wants a DNA test to determine her paternity.
"I think, first, you have to look at what his motives are," Stern told King. "If he honestly believed he was the father, based on when the baby was born, he should have handled it appropriately ... handle it through the proper channels, not through television and through the media."
Stern said he and Smith plan to marry "at some point."
"Right now we have to somehow get through what we're going through," he said, referring to the Sept. 10 death of Smith's 20-year-old son, Daniel, three days after his sister was born.