"I hadn't known [that Janet had a baby] - not for sure," he told the National Enquirer in a shocking new interview.
He claims one of the children is a woman in her 30s, who contacted him two years ago but they are yet to meet in person.
James, who was married to the star from 1984 to 1985, alleges her other secret child is a son who was also given up for adoption. Janet is yet to speak out about the claims.
"Her adoptive mother has passed away, but on her death bed, she confirmed the adoption," James added.
Meanwhile, James' mother, Etterlene DeBarge spoke to the publication and claimed she's seen photographs of who she believes is her other secret child, Omer Bhatti, who now works as a dancer and rapper in Norway.
Janet has spoken out about expecting her first child and believes it was 'God's will' whether she would ever be able to have children.
The iconic singer is expecting with husband Wissam Al Mana, 41, who she married back in 2012.
It comes after years of yearning to be a mum - all the while believing it would fall into 'God's hands' if it was meant to be.
She added: "I would hope my legacy would be bringing smiles to faces. Happiness with my music.
"Also, to make babies. I've had so many people come up to me and say, 'My child was conceived by listening to your music'."
Mirror Celeb has contacted Janet's rep for a comment.
