Jeanette and Patrick O'Donnell were overjoyed by the arrival of their firstborn daughter, Caitlin Carole.
But 2 1/2 years later, their baby girl still wasn't speaking. Then the O'Donnells received a frightening diagnosis: Caitlin was autistic.
The O'Donnells thought that if the condition was genetic, they wouldn't have anymore children. But they say that doctors assured them autism was not passed down from the parents' genes.
The young couple resumed their dream of having a big family. Along came Dierdre, Erin and Meaghan. They were a happy family, but then Erin stopped talking. Once again, doctors made the painful diagnosis: autism.
"By the time Erin was diagnosed, we already had four [children]," Patrick said.
And by that point, Jeanette was pregnant with their son, Patrick. Then the O'Donnells got an unplanned surprise, and little Kiernan came along.
One by one, the O'Donnells were given the same dreaded diagnosis. All told, the they have six children under their roof in Austin, Texas. Five of them fall on the spectrum of disorders called autism -- Meaghan is the only child who does not. Today, research shows a strong genetic component is at work with the disease.
An estimated 1.5 million people suffer from autism, which the Autism Society of America describes as "a complex developmental disability that affects an individual in the areas of social interaction and communication."
Autism affects each person differently and some have more severe complications than others. The O'Donnell children mirror the many distinct forms this complex disorder takes.
Dr. David Amaral, of the MIND Institute in Sacramento, Calif., says that studying these differences could change the way doctors treat autism.
"The benefit to the kids and to families will be that we'll be able to predict what will be the best treatment for a particular type of autism. Currently, we can't do that," he said.
Caitlin, 14, and Kiernan, 4, the eldest and youngest, are the bookends of the O'Donnell family encyclopedia of autism. They display hallmarks of the condition -- they walk on their toes, their bodies rock, arms flap, they often screech. Both are profoundly disturbed by certain environmental changes.
Amaral said if you asked the children why they were upset or frightened by certain situations, they wouldn't have any insight into it.
On the other end of the spectrum are Erin, 8, and Little Pat, 5, who can describe what they are feeling. Pat will hide his eyes from strangers, but says he does so because "he's nervous."
Both Erin and Pat made dramatic turnarounds.
"When I was about 3 years old, on my second day of school I started to speak," Erin said.
But they still have strong reactions to sensory stimulation. While Erin is soothed by bubbles on her skin, Pat is terrorized by running water.
And then there is Dierdre, the "quirky" one. She has a form of autism called Asperger's Syndrome. People with Asperger's will become obsessed with one particular subject.
"They'll go on talking about a topic of interest to them and not take any cues from you that you're not interested," Amaral said. "You still have at the core this deficit of social function."
Jeanette said it's painful for Dierdre to sit with the family and eat dinner. She prefers to eat alone, one item at a time.