JAMIE LYNN SPEARS, 16, and her boyfriend CASEY ALDRIDGE, 18, are engaged, Aldridge's cousin tells Us magazine. Aldridge proposed to the pregnant sister of pop princess BRITNEY SPEARS a "few days ago," according to Casey's cuz' TINA ROBINSON, who added that the couple aren't sure whether they'll tie the knot before or after Jamie Lynn gives birth. The expectant mom recently passed her high school equivalency exam.