"Devin is holding strong. Outwardly he's showing strength, but I don't how his emotions are internally," the twins' mother, Margi Coats, tells PEOPLE

It’s been about three days since Devin Coats, 18, said his final goodbyes to his twin brother, Nick. The Louisiana teen underwent a life-saving liver transplant in January — but his brother was not so fortunate.

“Devin is holding strong. Outwardly he’s showing strength, but I don’t how his emotions are internally,” the twins’ mother, Margi Coats, tells PEOPLE. “He knows that it’s an unfortunate situation that he had to lose his brother. But he knows Nick’s name and legacy will hopefully change the way our country is.”

The inseparable twin brothers were diagnosed with stage four cirrhosis of the liver, and both needed to be placed on the waiting list for a transplant. Although Devin underwent the Jan. 11 procedure, Margi says Nick wasn’t “sick enough” to be eligible for the waiting list. By the time he had secured a liver and was taken into the operating room, Nick had developed rare hepatic angiosarcoma, which spread beyond the liver.

Nick and Devin Coats twin liver transplantsCredit: Courtesy Coats Family
Devin (left) and Nick Coats
| Credit: Courtesy Coats Family

“[Doctors] couldn’t go any further because it was an inoperable condition at that point,” Margi tells PEOPLE. “I was devastated. I was overcome with the overwhelming feeling of sadness knowing I was going to lose my son. Had he not had to wait to be eligible to be listed on the donor registry, he would not have had the chance to develop angiosarcoma.”

She adds: “He did have a liver available, but because he had to wait in the beginning to be eligible to be listed, that’s what caused all of these problems … you have to get sick enough in order to get better and it shouldn’t be that way.”

Margi first revealed the news of Nick’s death in a post on a Facebook page dedicated to chronicling the twins’ journey. She said Nick “fought hard to have a new chance at life,” and described him in a post as “strong” and “courageous.”

Nick and Devin Coats twin liver transplants Credit: Courtesy Coats Family
Nick (left) and Devin Coats
| Credit: Courtesy Coats Family

“Nick was my protector and he loved his family,” Margi continued. “Nick showed others his genuine heart and was a good friend to many.”

On a GoFundMe page set up for the family, Margi explained that Nick first exhibited symptoms of illness with pain in his legs. She said she first chalked it up to “growing pains.”

Nick and Devin Coats twin liver transplants Credit: Courtesy Coats Family
Nick Coats
| Credit: Courtesy Coats Family

On their GoFundMe page, Margi explained that it was Nick who first exhibited symptoms with pain in his legs that she at first thought were “growing pains.” Now, Margi says she’s dedicated to encouraging the public to become organ donors so “people who are dying on a daily basis won’t have to wait anymore.”

“You cannot take your organs to heaven, heaven knows we need them here,” she tells PEOPLE. “Nick has now had to pay his price in life. Nick’s in a better place. He’s singing. He’s rejoicing. He’s encouraging me to move on with this. He knows he’s got a strong mother.”