In January, Fivecoat, now 62, was getting bloodwork done at MD Anderson Cancer Center in Houston when she got news that would upend her own battle with cancer.
Across the street from MD Anderson, at Texas Children's Hospital, Fivecoat's then-nearly 1-year-old granddaughter Whitney was diagnosed with leukemia.
"It was the most surreal thing," Fivecoat told "Good Morning America," adding that she was with Whitney's paternal grandmother at MD Anderson when they dropped everything to run across the street. "We were literally running from MD Anderson to Texas Children's, trying to just get there."
At Texas Children's Hospital, Fivecoat's daughter Shelly McAfee and her husband Tyler McAfee were given the news that their seemingly healthy toddler was battling acute myeloid leukemia, or AML, a cancer of the bone marrow and the blood, according to the National Cancer Institute.
"Our hearts fell to the floor," Shelly McAfee said of hearing the diagnosis. "My husband and I, we just melted."
The McAfees said they had noticed some swelling and bruising around Whitney's eye that then spread to her other eye, leading them to seek medical care.
After receiving their daughter's AML diagnosis, the couple's lives were quickly turned upside down. Whitney immediately began chemotherapy, which required the McAfees, also the parents of a 4-year-old son, to stay at Texas Children's Hospital, a two-hour drive from their home in Port Lavaca, Texas, for over 40 days.
Around the same time, across the street from the hospital, at MD Anderson, Fivecoat began chemotherapy for breast cancer.
"My mom's chemo schedule fell on a Friday, so there were times where my mother-in-law would bring her to treatment, and they would actually stay with Whitney, and both my husband and I would be at home with our son," Shelly McAfee said, adding, "It was a good time for her to be there, to hang out with Whitney, but also a time to rest, and in the event that she didn't feel great or needed to go back to MD Anderson, she was right there."
Over the next several months, grandmother and granddaughter would go through the unfortunate side effects of chemotherapy together, like losing their hair.
"It reminds you how fragile life is, and that it doesn't obviously matter how old you are or what stage you are in your life, you never know what the next stage will bring," Tyler McAfee said of watching both his daughter and his mother-in-law battle cancer.
When Fivecoat needed strength or reassurance that things would be OK, she said she found it in Whitney, including when they both had to take the same particularly aggressive course of chemotherapy.
"When you know that your granddaughter, who at that point wasn't even a year old, has already done that treatment, it made me realize, 'You know what, I can do this,'" Fivecoat said. "There were several different instances where I was scared about what I had coming up, and Shelly would go, 'Mom, Whitney's already done that.' So I'm like, 'Well, OK, I can do this too, you know.'"
Fivecoat was right by her granddaughter's side in June when Whitney underwent a lifesaving bone marrow transplant thanks to an anonymous stranger who signed up to be a donor and was found to be a perfect match.
Just two months later, in August, Whitney and her parents supported Fivecoat as she underwent a double mastectomy as part of her breast cancer treatment.
"I'm not really sure how we would have all gotten through the last six months without each other," Fivecoat said of her family, including her son-in-law's family and her younger daughter.
Shelly McAfee added of the support they've provided each other, "When they say it takes a village, I mean, you don't realize that you need the village until you're in a unforeseen circumstance like this."
Whitney's doctor, Dr. Erin Doherty, pediatric oncologist at Texas Children's Hospital, said she's never before in her career seen a grandmother and granddaughter go through chemotherapy at the same time. She said though Whitney's and Fivecoat's cancers are completely unrelated to each other, she saw firsthand the support they provided each other.
"Having that family support is really important," Doherty told "GMA." "Whitney would just light up whenever she saw grandma and grandpa, and all her family members who visited her, so it definitely helped her kind of forget about what was going on while she was in the hospital."
Now nearly one year after their dual diagnoses, both Whitney and Fivecoat are moving forward.
Fivecoat said she has around eight more chemotherapy treatments left to go, followed by breast reconstructive surgery.
Whitney, now 19 months old, has responded well to her transplant, and while she will continue to be monitored, Doherty said she should live a "long, healthy life."
The McAfees describe Whitney as "amazing," a word they also use to describe the friends, strangers, and especially family who have helped them over the past year.
"Naturally, we want to take care of things ourselves and not depend on other people, but having to go through this and having to depend on other people, it's just very, it's very humbling," Tyler McAfee said. "But it also gives you a whole new level of appreciation and love for other people."