Singers Rihanna and 50 Cent have teamed up to help a struggling couple save their ailing baby daughter, who is in dire need of bone marrow transplant. One-year-old Ayelet Galena suffers from a life-threatening congenital disorder. Rihanna and 50 Cent have signed up for a blood test to determine if they could be donors. Both have also called on their fans to follow suit, reports dailystar.co.uk.