FOXBORO — An incurable disease. An unlikely friend. An unbreakable bond.

That’s the gist of the relationship between Patriots undrafted rookie cornerback V’Angelo Bentley and 10-year-old Colby Crowley, but their connection really has been woven by inspiring details, messages of encouragement and, sometimes, hilariously brutal honesty.

Crowley was in kindergarten when his older brother, Noah, was diagnosed with X-linked juvenile retinoschisis. Because it’s an inherited disease, doctors at Northwestern University tested Colby and uncovered the same recessive trait. The rare disease will progressively degenerate their eyesight through young adulthood, stabilize for a while and then take another decline later in their lives. It’s a challenge for them to see in the dark, watch TV, text friends or use a computer. Eventually, they’re expected to be legally blind. Even with glasses, Noah has 20-80 vision, and Colby has 20-70.

“It was a punch in the gut,” their mother, Jennifer Crowley, said of the diagnosis.

About two years later, Colby told his mother as they were driving to school that his vision was blurred by blood in his right eye, so they rushed back to Northwestern. Doctors said he suffered a hemorrhage, and he wouldn’t be able to run, jump, go out to recess or play sports. Like a snow globe, sudden movement would cause the blood to worsen again until the hemorrhage was gone a year later.

“That was a killer for Colby because he was counting down the days to play football,” Jennifer said. “He’s got the fire in him, and he could have definitely hit somebody. He just loves it. He’s all boy. He’s rough and tough and waiting for it to happen. For that to get taken away from him was pretty tough. It was pretty hard.”

The hemorrhage wiped out the peripheral vision in Colby’s eye, so football was completely off the table. But in 2014, as Colby was roaming a youth field in Champagne, Ill., as an honorary assistant coach for Noah’s football team, Bentley arrived to teach kids about the game.

Colby already was a huge fan of the University of Illinois cornerback, so he fearlessly marched over to introduce himself. Bentley asked his new friend why he wasn’t wearing pads, and he was consumed by Colby’s story.

“He lights up the room,” Bentley said. “His excitement, the joy he brings, it can touch you.”

They played catch and ran around a bit — legend has it Colby might have beaten Bentley in a race — and Colby introduced Bentley to his friends. It didn’t even take an hour for Colby’s charm to inspire Bentley, who grabbed the Crowleys’ contact information before returning to the university.

Bentley informed then-Illini coach Tim Beckman of his desire to do something nice for Colby, and Beckman emailed the Crowleys that night to invite the family to the Illini season opener. Colby would serve as the grand marshal, march in the parade with the players, hang out on the field and watch the game from premium seats, which was particularly important because of his diminished vision.

“It was the time of his life,” Jennifer said. “It was awesome. We were so grateful.”

Bentley far exceeded the Crowleys’ expectations. And really, it could have ended there, and the story would have been beautiful.

But friendships don’t end, and that’s what is so genuine about V’Angelo and Colby. About six weeks later, Colby asked his mom to invite Bentley to his ninth birthday party at a bowling alley. The scheduling was actually perfect, as it was Illinois’ bye week. Then again, this was a college kid with a weekend off. He wouldn’t actually show, would he?

All it took was a text.

“He could have gone home. He could have done anything else,” Jennifer said. “Not only did he come, but he hung out with all the kids, gave everybody autographs, had some pizza, got Colby a game ball. (Bentley) is just an awesome kid.”

Bentley remains in regular contact with the Crowleys, speaking as recently as yesterday. He’ll reach out during the holidays or a random afternoon just to see how Colby and Noah are doing.

A few months ago, Colby was his school’s fourth-grade “star student of the week,” and guess who he invited to speak to his class? And when Colby recently was cleared to play soccer, guess who outfitted him with an Illinois backpack? And when the Crowleys spoke to Bentley 13 days ago before the final day of the NFL draft, guess who predicted where Bentley would end up?

No, seriously. Colby is a Patriots fan in the heart of Bears country.

“I said, ‘Where do you think (Bentley) should go, buddy?’ ” Jennifer recalled. “(Colby) was giving (Bentley) some teams, and he said, ‘I would love for him to go to the Patriots.’ And Colby is not shy. He is frightfully honest. He said to V’Angelo, ‘The only thing I’m worried about is you’d be like second- or third-string because they are super-duper good. I’m kind of thinking you should go somewhere where you can get more playing time.’ ”

Bentley already has the inspiration. That speech secured more than enough motivation.

“Come out here and keep working hard every day, knowing he may never play (contact) sports again, you always want to go out there and play hard for him,” Bentley said.

Now that’s a true friend.