At 8 months old, Joshua and Jacob Spates continue to fight but, according to doctors, they have already beaten the odds.

They were delivered by Caesarean section in January at Bonheur Children’s Hospital in Memphis, Tenn., three weeks early and conjoined.

Conjoined twins only occur in approximately one in 100,000 births. Moreover, the brothers were attached to each other at the lower spine and pelvis, an unusual connection that made them what are known as pygopagus twins. Only 15 percent of conjoined twins are connected in this way; in a press statement, the hospital noted that the twins are one of only six such cases documented in Memphis history. Even before their birth, doctors could see in X-rays of their mother’s womb the challenges that would come should they dare to attempt separation surgery.

Yet, surgeons decided to go forward with the life-or-death operation last month. When doctors finally separated them, on Aug. 28 after a 13-hour surgery, they became one of only two dozen set of conjoined twins in the world to be successfully separated. The operation involved the delicate detachment of the spinal cord and column, as well as muscles and other tissues.

Joshua and Jacob are not completely out of the woods yet; each has begun life with a laundry list of medical conditions and complications, including problems with their hearts and other organs. They are expected to remain at the hospital for some time while they recover, and they will receive clinical care and rehabilitation therapy until they are healthy enough to go home.