If commander Curt Brown counts noses to make sure all crewmembers are aboard shuttle Discovery, he might find himself glancing a bit longer than usual at his co-pilot. It wouldn’t be the first time astronaut Scott Kelly would fall under close scrutiny, nor is it likely to be the last.

Kelly, who will be making his first flight into space, shares a surname, face and physique with another shuttle pilot, Mark Kelly, his identical twin brother. Even the smart folks in the astronaut office have problems telling the Kellys apart.

"People make mistakes all the time," says Mark, who is awaiting his first flight assignment.

Not that he is not capable of this kind of deception. Aside from looking alike, the brothers are ace Navy test pilots, who were selected at the same time by NASA to become astronauts, and trained in the same class to learn to fly the shuttle. Even among friends as a practical joke, Mark and Scott wouldn’t try to fool people.

"Everybody says "Oh, you should take your brother’s place on the flight." We’re like, ‘Aughh!’ I’ve been listening to this for 35 years,’" says Mark. "We never did that trick just because people would ask us to."

Growing up in New Jersey, Mark and Scott -- the only children of a pair of police officers -- started dreaming of spaceflight in high school. It was 1981 and NASA was just beginning space shuttle flights after a six-year hiatus in human space expeditions.

"I don’t remember talking about it a lot with him," says Mark. "But it was something I was interested in. I think he was too."

After graduating from Mountain High School in West Orange, N.J. in 1982, Mark headed to the U.S. Merchant Marine Academy for a Bachelor of Science degree in marine engineering and nautical science. Scott enrolled at the State University of New York Maritime College, where he earned a bachelor’s in electrical engineering.

The Kellys followed similar but distinct paths to become naval aviators, then reunited at the U.S. Naval Test Pilot School in 1993. Upon graduation, they were both worked as test pilots at the Strike Aircraft Test Squadron, Naval Air Warfare Center in Patuxent River, Md. Mark was assigned to the U.S. Naval Test Pilot School as an instructor pilot when he was selected to become an astronaut. Scott was still in Maryland flying experimental aircraft.

"Everybody we were working with, just about, were putting in their applications (to become an astronaut) so I knew he was doing it, just like I knew everybody else was too," said Scott, in a preflight interview.

For Mark, it was the second application that scored an interview and invitation to join the elite astronaut corps. Scott made it in on his first try.

"I though we both had about the same chance," said Scott. "I guess I thought in the back of my mind if one of us was going to get accepted, maybe, perhaps, they would accept us both," said Scott.

Or neither, said Mark. "Just ‘cause of the odds. It’s pretty tough to get an interview. Then we both realized there was a chance that one would get selected and the other wouldn’t, but we both had strong backgrounds in comparison to everyone else."

Mark isn’t jealous that Scott is getting to fly first in space. "One of us was going to hve to fly first," he says, practically. Scott offered to fly a souvenir for Mark, but he declined.

"I figure I’ll be flying myself here hopefully in a year or so," he said.