A baby boy from County Kerry has baffled doctors by reaching 20 months without developing. He has never sat up, rolled over or held anything in his hand. His twin sister, born just one minute later, is completely normal for their age.

On September 21, 2009, Sean O’Shea was delivered by cesarean section. His twin sister Keelin was born just one minute later.

Now 20 months on, Sean has failed to reach any developmental milestone, while Keelin is walking and talking like a normal toddler. The  medical world is baffled.

John and Collette O’Shea, the twin’s parents, from Headford, Killarney, County Kerry, said the pregnancy was completely normal but within four of five weeks of the birth they realized that there was something different about their son.

Collette told the Irish Independent : “Keelin was developing like a normal baby and becoming more alert and responsive but there was nothing from our little man.

"We took him to Dr Leahy at Kerry General Hospital who immediately knew there was something wrong and sent us straight away to Temple Street, where we've been going since.

"They just can't seem to pinpoint what's wrong with him.

"What's puzzling them is how one of the twins is perfect and one isn't."

She continued “They know he's lacking white matter in the brain but they say the longer it goes undiagnosed, the more likely that it's something very rare ... If we knew, good or bad, what's going to happen down the road that would be something."

Although Sean appears lifeless, Collette is convinced that he his aware of his surroundings and his family. She said “There is a definite bond between twins, and Keelin always manages to get a smile from him. So does Chloe [their eight-year-old daughter], who's like a mother hen over him.”

"He also responds to a little toy ambulance we got him that makes a noise like an ambulance, but if you drop something and make a loud bang he doesn't respond.

"At least we've started looking for answers when he's young, so hopefully they'll be able to find out what's wrong with Sean and put a name on it finally.”

John and Collette are currently setting up a charity to help them meet the cost of Sean’s medical expenses as doctors try to figure out what is wrong with their little boy.

Currently Sean requires around the clock care. Collette explained: “Sean is oxygen dependent at night, or any time he's asleep, and needs a ventilator. Otherwise, he can stop breathing. He also needs suctioning to clear his airways."

Sean also attends physiotherapy at Enable Ireland one a week and nurses provided by the Health Service Executive and the Jack & Jill Foundation tend to him at home for two days a week.