Doctors told Katherine Mitchell she wouldn't live past the age of 15.
"I never really understood it until a couple years ago," Katherine added.
She was only in 7th grade when she found out she had Marfan Syndrome, Celiac Disease, epilepsy and heart disease. Katherine is 16 now.
Katherine said, "I would show my mom puppies, pitbull puppies and she'd be like, 'no'...and then I found Roman and he had all the same diseases and stuff that I had."
Roman was only supposed to be around for three months.
"He lived to be ten months," said Katherine.
"It was the saddest day when he passed away," said her mom, Carol Mitchell. "I think we mourned for maybe, two weeks and just didn't function for two weeks, because it kind of let us all know that we're gonna have to live through this again, only with Katherine."
Roman inspired Katherine to create a bucket list.
Carol said, "The one amazing thing about him, which is also the same thing about Katherine, is that their hearts are not perfect, but they love with their whole heart."
What started off as volunteering at animal shelters, turned into Roman's Rescue, a non-profit organization aimed at saving animals scheduled to be euthanized.
"There's this do that has three days, or a day and we'll go pick them up...and we'll start training them and getting them socialized and then eventually when they're good with kids and cats and everything, then we find them a home," said Katherine. "I want to start doing adoption events. I want to get bigger. My dream is to get a TV show, like Pitbulls and Parollees or Pitboss, that's my dream."
Carol said, "There is no family history of anything she has and she has three other siblings that are perfectly healthy."
They call her "the chosen one."
"She will end up dying from a heart aneurysm and there's nothing we can do to stop it," said her mom. "She tweeted that she was glad all these things happened to her because she could handle it."
Roman's Rescue will live on, as Katherine's legacy, after she passes.