This Eagles fan needed a kidney. A Chiefs fan volunteered.

For two men — one an Eagles fan and the other a Chiefs supporter — a bond runs far deeper than their favorite teams’ forthcoming showdown in Super Bowl LVII.

Billy Welsh, of Cherry Hill, and John Gladwell, of Kansas City, Mo., met on a military base in 2001 while serving in the Marine Corps.

Gladwell, then a Marine with years of experience under his belt, admitted he wasn’t too fond of the incoming recruit Welsh and his northeastern attitude. But today they share two things: a newfound football rivalry and a kidney.

“It’s literally life-saving,” Welsh, 39, said of his friendship with 44-year-old Gladwell.

After their brief overlap in the Marines, the two went nearly 20 years without speaking. That changed in 2019, when Welsh announced on Facebook that he was diagnosed with polycystic kidney disease, a genetic disorder that often requires a transplant to prevent eventual kidney failure.

Welsh needed a kidney fast, and Gladwell came across the post.

“I’m like, ‘What’s your blood type, I’ll check and verify mine,’” Gladwell said. “Two hours of looking through medical records, I finally found it. I’m like, ‘Hey, I’m a match … let’s do what we have to do to get this started.’”

After getting blood work done, Gladwell was amazed to find he was indeed a 99% match, and began making plans to have his kidney removed in Kansas City and shipped to Welsh at the Nicoletti Kidney Transplant Center in Philadelphia.

Some logistical complications meant that plan wouldn’t end up working, so he and Welsh agreed that Gladwell should fly to Philadelphia and have the procedure done.

In October 2020, Gladwell and Welsh both successfully went under the knife.

When Gladwell woke up, he remembers asking doctors, “Where’s Billy?”

“I refused to go to sleep until I saw them wheel him by,” Gladwell said, mentioning the unwavering brotherhood he felt with his fellow Marine even though they’d butted heads in the past.

“He’s definitely my brother from another mother,” Welsh said of Gladwell. “All Marines are like that. If any of my other brothers came through and needed one of my organs ... I would. We can pick up where we left off without missing a beat.”

The two would keep their friendship alive through football, when the Chiefs came to Lincoln Financial Field to take on the Eagles in 2021.

Gladwell, who now works as a security guard for the Chiefs, flew back to Philadelphia and watched the game with Welsh and Welsh’s family. Gladwell remembers the stark difference between the bright red worn by him and his wife and the green jerseys surrounding them.

When the teams meet again on Feb. 12 in Arizona for the Super Bowl, Gladwell will remain in Kansas City. Still, he said he expects “back-and-forth” bickering with Welsh over the phone.

“The Battle of the Kidneys,” Welsh dubbed the game with a laugh. “Definitely going to be FaceTiming John.”