MILFORD — Declan Harmon is a 4-year-old boy.

Like many others his age, among his loves are “cuddles and superheroes,” according to his mom, Cheri Harmon. Spider-Man is his all-time favorite. At the moment, though, Declan is big into Godzilla and King Kong.

He also likes dancing at Nanticoke Indian powwows, as his father, Matt Harmon, is a member of the tribe.

And while Declan’s big sister, Brittany Dundas, 24, describes her brother as “feisty,” he’s also very caring.

For example, at the end of one of Declan’s frequent visits with his sister — they live in the same Milford neighborhood, just across a parking lot — Ms. Dundas remarked that she was unhappy to see him go.

“He was like, ‘I want to stay with you. I don’t want you to be sad,’” she said. So every visit following, Declan checked in to make sure it was OK if he departed.

The youngster also loves jokes, Ms. Dundas said, and reciting them to nurses is one way he copes with his treatments for Fanconi anemia, a rare and devastating genetic disorder. It requires twice-weekly visits to the hospital for blood transfusions.

The condition is the reason behind Declan’s small frame. It was also what caused bruises to start appearing all over his body earlier this year, his family would later find out.

Ms. Harmon at first wondered if maybe Declan’s brother was playing too roughly with him. But the bruises started happening more frequently, she said.

An Aug. 4 trip to the pediatrician and some bloodwork followed. “What’s it going to hurt? It’s probably nothing, but I need to do it,” she thought at the time.

But she knew something wasn’t right when she received a phone call from the doctor on a Saturday morning.

She said the doctor started with, “Look, I don’t want you to panic,” but then shared that Declan didn’t have enough blood cells. She was advised to take him to Nemours Children’s Health in Wilmington for a transfusion and to start running tests.

A few days later, after doctors had ruled out leukemia, they diagnosed Declan with aplastic anemia, signifying that his body could not produce blood cells on its own. Or as Declan, who quickly picks up slang, put it to his mom: “My bone marrow took an L” — “L” meaning “loss.”

A couple weeks later, the doctors discerned the underlying condition to be Fanconi anemia. By chance, Declan had received copies of a recessive gene that causes the condition from each of his parents.

Ever since, Declan has been getting his blood transfusions, but they are not enough. His doctors say he needs a bone marrow transplant from a match in two to three months, Ms. Harmon said.

Many have asked if they can be tested to see if they are a match for Declan. And while Ms. Harmon would never discourage someone from doing so, that process would almost certainly take too long to help her son.

However, he has been designated a high priority on the bone marrow registry. His medical team is trying to find a perfect match but will settle for as close to perfect as they can get, she said.

With the transplant, Declan could live into his 20s. Hopefully, by then, his mother said, research will have uncovered more ways to help people with Fanconi anemia.

“My goal is for him to outlive me. That is what we’re hoping for,” said the 44-year-old.

Meanwhile, there are ways others can help right now.

The restaurant and distillery easySpeak spirits has started a fundraiser to help pay for the family’s expenses on GoFundMe. Though Declan’s medical insurance is paying for most of his care, other costs are adding up. His mother, for example, has essentially put her cleaning businesses on hold to spend more time with him.

On Oct. 23 from noon to 5 p.m., easySpeak will host an event on behalf of the Harmons. Attendees can partake of a variety of activities, including a silent auction, a raffle for lower-level tickets to an Eagles vs. Titans football game and more, said the restaurant’s executive assistant, Ashley Burns. Some of the proceeds from craft cocktails sold that day will be donated, as well. Plus, there will be fun for children.

Marissa King, easySpeak’s owner, summed up the reason for her business’s participation: “We’re rooting for (Declan), and we’re praying for (them).”

EasySpeak is looking for sponsors to help with the fundraiser. Anyone interested can email Ms. Burns at ashley@easyspeakspirits.com or text 302-858-1875.