It was a particularly special Father’s Day for a Port Washington family.

Eighteen-month-old Benjamin Carstens was just a few days old when he was diagnosed with OTC deficiency -- a rare metabolic disorder which can be life threatening.

“We were completely destroyed,” said Brian Carstens, Benjamin’s dad. “I mean, we were very worried we weren't going to have him with us.”

“You never think that it's going to be you or your family,” said Karla Hernandez Garcia, Benjamin’s mom. “When my son was first diagnosed, I felt like my world was coming to an end. I wasn't sure if I was truly going to live that happily ever after of having a beautiful, healthy family.”

Benjamin spent a lot of time in the hospital during his first year of life. It was a small miracle when his dad found out he could be a living donor.

“The surgical procedure for children with metabolic disease can be some of the most technically challenging because they're done when they're very small,” said Dr. Adam Griesemer, the surgical director of pediatric liver transplants at Hassenfeld Children’s Hospital at NYU Langone.

In August, on his birthday, Brian underwent surgery, giving part of his liver to his son.

“I don't think there was any hesitation when he heard that he could do something to help save his son,” said Dr. Jennifer Vittorio, Benjamin's pediatric hepatologist and medical director of pediatric liver transplant.

“It’s completely surreal,” Carstens said. “We really didn't think that he would be with us after the initial crises, and we're blessed. We feel blessed every single day that we have him.”

Today, both father and son are nine months post-transplant, happy and healthy, and able to celebrate another Father’s Day together as a family.

Benjamin still has a feeding tube and a lot of medical checkups, but doctors say he’s expected to make a full recovery and be able to live a normal life.

“They're both my entire world,” Hernandez Garcia said. “And to think back that there was a time where I didn't think this was going to be a reality, our family being together. I truly am eternally grateful.”