Juvenile Wants Paternity Test To Get Custody of His Son

Juvenile recently filed court docs, demanding the test ... claiming he never established paternity when his son was born and didn't even sign the birth certificate at the time.

He also claimed the boy's mother has had sexual relations with other people ... so there's a chance he's not the real daddy.

But despite what he said in the court papers, Juv tells TMZ ... "My son acts and looks just like me. I am doing this for procedural reasons to get custody."

What complicated the matter even more ... Juvenile owes $160,000 in unpaid child support ... so if the test proves the kid ISN'T his ... he could be off the hook.