Now KELIS is keeping Nas from his Son...WOW!!

Nas says his estranged wife Kelis is keeping him from seeing his son Knight as much as he'd like. He tells Vibe.com, "When his mom feels in the mood she sends pictures. If not, its hell...trying to figure that out, trying to get him... A man shouldn't go through that...but it's another story I'ma tell at a different time."

Nas, who has a 16-year-old daughter from a previous relationship, adds, "My daughter is my princess and now I have a prince... It's the coolest [thing] ever."

Distant Relatives -- Nas's collaborative disc with Damian Marley -- arrives next week.