They share nearly everything.
Siblings Tommy and Emily Walters are close, in the way one-year-olds can be.
"They're very sweet babies,” said their mother, Charise Walters. "They do actually, I think, care about each other and I think they really enjoy each other's company."
Last year, their parents, Charise and Mike Walters, got a double-dose of surprising news.
"I had made the comment jokingly, like, 'Oh, we can handle a baby, it's not like it's going to be twins or anything,'” Charise said. “And then, found out in my ultrasound that I was having twins and was really thrown back."
She was thrown back - and then, taken aback - when they learned Emily would be born with a serious birth defect: congenital diaphragmatic hernia.
"In that case, the diaphragm fails to develop," said Dr. Ken Liechty, Emily’s pediatric surgeon at Children's Hospital Colorado.
For Emily, that meant her lungs couldn't develop properly and her heart was growing in the wrong place. The condition affects one out of every 2,500 births. At Children’s Hospital, they have a more than 80-percent survival rate – but Emily’s case was severe.
"We still had some very frank conversations that she may not survive," Dr. Liechty said.
Her chance of survival was less than 20 percent.
"We did as much as we could mentally, to prepare – and we held off buying a few things, too, because we didn't know what to expect," Charise said.
The twins came six weeks early last November. Tommy made it home for Christmas last year. Emily did not.
"Last Christmas, here at the hospital, we set up a tree," Charise said.
Emily would spend another four months undergoing surgery and therapy to help her live - and that she did.
"She beat all odds to survive and be here," Dr. Liechty.
Now, for the first time, the Walters family will be together at Christmas…
"We saw Santa Claus yesterday," Charise said.
It’s a holiday gift for Emily and her family, who say they'll treasure every Christmas together, especially after knowing what it's like to be apart.
"But when we're home now, every Christmas, when we put up the Christmas tree, we'll think of that," Charise said.
Children's Hospital Colorado says overall, Emily is well on her way to recovery. They hope to get her off her oxygen device by February.