There've been over 40 million births this year (and counting). Extrapolating the rate of 1 in 50,000 to 1 in 200,000 conjoined births in the United States every year, only about 200 to 800 conjoined twins are born annually in the world. In the U.S., the survival rate is around 50 percent.

About nine months ago in Texas, twin boys were born attached to the hip and breast bone. They shared several organs. Doctors didn't think they'd survive, but on Thursday, they were released from the Dallas hospital that has so far been their only home, ABC News reported.

"You can never predict what can happen but these little guys are definitely survivors," Dr. Tom Renard, the lead pediatric separation surgeon, told ABC.

The twins won't move to their official homes yet. Instead, they'll go to a rehabilitation facility for a few more months.

The babies, who shared the same liver and intestines, can't breathe or eat on their own yet (no timeline availlable for that milestone), but they no longer need around the clock care from doctors and nurses.

Separating a shared blood vessel in the liver was the most difficult part of surgery, according to Renard. Now, the main concern is infection.

For the boys' father, also the father of a two and seven-year old, the greatest challenge will be managing the twins' day-to-day needs.

"I'll finally have my family together but we are about to face some serious challenges," he said. "The really frightening life-or-death stuff is behind us but now we worry how about how we are going to pull the rest of it off."