If James, Jr he is deceased, you won't need to locate his SSN. Fill out the form at this link: http://www.ssa.gov/online/ssa-711.pdf

If you don't think he is deceased, you will have to go this route: http://www.ehow.com/how_5503821_missing-person-through-socia... and pay strict attention to what you can and cannot say in the letter.

Good luck.