Toddler Owen and little brother, Cooper, love to play with blankets.
Turned loose in their living room last week, the two got a hold of several and used them to hide.
"As you can tell, they're still rough with each other," said their father, Al Peterson. "Cooper gets a big smile on his face whenever he hears Owen coming down the hall."
Those moments are a welcome break from the hours the family spends every week at the Sanford Health pediatric clinic.
Cooper has neurofibromatosis, a disease that affects the nervous system and causes tumors to grow. It led the 13-month-old to develop optic gliomas, which are brain tumors on the optic nerve.
The aggressive tumors have caused his vision to deteriorate. Though they are not cancerous, he needs chemotherapy weekly to halt their growth.
Al and his wife, Tiffany, had never heard of the disease before they suspected their son might have it.
"Initially it was heartbreaking because you don't know what could go wrong," she said. "You hear a big word like that and assume the worst."
When they got the diagnosis two months ago, they drove from Mandan to Minneapolis the next day to visit the University of Minnesota Masonic Children's Hospital. They need to make trips there every few months over the next several years until Cooper's disease stabilizes.
Tiffany Peterson said she has learned to adapt to ever-changing situations.
"You have to roll with whatever comes at you," she said.
She says she hopes to return to a more full-time work schedule at Sanford, where she is a nurse. She had to drop to only one day a week so she can care for Cooper.
The North Dakota State Library, where Al Peterson works, also has been flexible. He said friends and family have made meals, baby-sat and given money to cover expenses.
"We are overwhelmed with the amount of support," he said.
Owen shows his sweet side, too, when it comes to his brother.
Take the other day, for example, when their mom had to stop playing with the boys for a minute. Cooper became upset.
"Owen came to him with a book and said, 'I've got you. I've got you," and sat down and read a story to him," Tiffany Peterson said.
The two enjoy playing with blocks together. But, like any little brother would do, Cooper sometimes tries to smash Owen's toy robots.
This Mother's Day, the Petersons look forward to spending time with their boys and Al's mother, who's flying in from Pennsylvania.
Weather permitting, they'll spend the day in the yard out back where they have a playground set up for their kids to go wild.
"It's a free show," Al Peterson said, laughing. "It's always funny."