Ness with, from right, Cheston, Chatham, Chance and a portrait of Chesley at home in Massachusetts.Photo: Anjelica Jardiel

Amy Ness rollout 4/24

“If I am to break down and not be able to do anything, my babies will suffer,“Ashley Nesstells PEOPLE in this week’s issue, where she shares photos documenting their new life at home for the first time. “I feel like I’m just that person that has to hold everything together.”

“I have to take care of myself so I can take care of them,” she says. “And they definitely are keeping me strong.”

Ness, 36, a part-time hair stylist, has an ally in her partner and the newborns' dad, Val Bettencourt, 48, a small-engine mechanic. The couple’s three-bedroom abode in Taunton, Mass., is also home to a daughter, Chanel, 9, and sons Isaiah, 11, and Zayden, 8.

During the months that daughter Chesley — who was born at 1 lb. 7 oz., the smallest of the four preemies — spent in the Neonatal Intensive Care Unit (NICU) at Mass General for Children in Boston, Ness “was that little girl’s voice,” Bettencourt says.

“When I’m around, she’s tough,” he says of Ness. “But I feel for her the most. I don’t know what happens with her when doors are closed.”

Says Ness: “I don’t allow anyone to see that.”

For more on Ashley Ness, pick up the latest issue of PEOPLE, on newsstands Friday, or subscribehere.

Ashley Ness with her late daughter Chesley.

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Herunique pregnancywas a “1 in 10 million” event, according to Dr. Ahmet Baschat, director of the Johns Hopkins Center for Fetal Therapy, who was not involved in Ness’s care. The phenomenon occurs when two eggs are fertilized at the same time, and then each fertilized egg divides again, resulting in two sets of identical twins.

Chesley and her twin sister Chatham, along with twin brothers Chance and Cheston, were delivered about 12 weeks early via Cesarean section on July 28. All but Chesley were discharged separately in October. Chesley faced hurdles the others did not, and as her mother held her at the hospital, she died Feb. 22, having never beaten the setback of lungs that failed to develop fully.

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Amid the heartbreak, Ness has also received support from daughter Chanel, 9, who became “a mother hen” to her little siblings.

Now Ness — who previously said Chesley “has shown me more about life, love and serenity than I ever knew” — hopes to transition her grief to be a support for other parents facing difficult decisions about their child’s care.

Chanel’s loving tribute to her late sister Chesley.Courtesy Ashley Ness

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Ness “was one of the most dedicated, open-minded, attentive mothers we have seen,” says NICU medical director Dr. Rodica Turcu. “The fact is there was no day since the babies were born when Ashley wasn’t here. It meant the world for all four.” As a result, she “will be a great advocate,” Dr. Turcu says. “Because she understands.”

And while Ness weighs what shape that role may take, she knows she will teach her babies all about their sister.

“It’s hard to remember life without our babies,” says Ness (with Chance and Chesley’s picture and, clockwise, Chatham, Chanel, Zayden, Isaiah, dad Bettencourt and Cheston).Anjelica Jardiel

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“Honestly, I speak about Chesley every day,” she says. “All three of the babies, they’ll look up at the ceiling, always in my bedroom, and they’re always talking, talking, talking.” (The family is also continuing aGoFundMe campaign, hoping to build a home addition so they can move the infants out of their bedroom.)

source: people.com