Gap-tooth giant Michael Strahan is at the center of a shocking love child scandal! RadarOnline.com can reveal a 21-year-old man — given up for adoption at birth — is convinced Michael is his father. But the 44-year-old former NFL great has refused to recognize the man as his biological child!

David Brown is Strahan’s strapping mirror image, and believes he was born after the Good Morning America co-host knocked up a lover before marrying his second wife, Jean Muggli, in 1999.

“I know it in my heart,” Brown told Radar. “All of the facts point in that direction. If Michael were sitting in front of me now, he would know, too.That’s why I think I got the run-around.

At an athletic 6-feet-4 and 240 pounds, Brown bears an uncanny physical resemblance to the former All-Pro New York Giants lineman, who stands 6-feet-5 and weighs about 255 pounds. He also has Brown’s twinkly brown eyes and famous gap-toothed smile.

Brown even played football at the same defensive line position as Michael at a New Jersey high school — and dreams of following in his father’s NFL footsteps.

“I know I have it in me,” Brown told Radar. “My explosiveness off the ball is just like Mike’s!”

But Brown said the real link to the Fox NFL Sunday analyst is in his blood.

Brown was born at St. Luke’s Roosevelt Hospital in New York City on Dec. 31, 1994, and immediately put up for adoption by his biological parents.

A birth certificate obtained by Radar does not list the names of those parents, only the adoptive couple who raised him — Pentecostal ministers Bobbi Brown, 67, and John Brown, 57.

But Radar was able to obtain records from the adoption agency — Spence-Chapin Adoption Services — that offer more detail.

According to the documents: “Your birth mother was 19 years old when you were born. She was very tall and slender. . . She enjoyed reading and embroidering and running track.”

Strahan has often been accused of having a wandering eye while married. In August 2014, it was revealed how Muggli accused Strahan during their bitter 2005 divorce rumble of cheating — and even using a hidden camera to videotape her sister while she was in their home.

Over the years, Brown was often asked about his resemblance to Strahan, but said he didn’t give the idea much thought until his high school football coach suggested he start digging.

Brown recalled the moment his obsession took hold — and he set out to learn the truth.

“I was lying in bed and had the NFL Channel on in 2015,” he told Radar. “They were broadcasting the Giants’ Super Bowl victory over the Patriots and I kept hearing Mike’s name. Something told me, if he’s your dad, find out. So I Googled it. . . . I had this voice in my head saying, ‘Keep going. Keep looking. Keep pushing. There’s something here for you to find.’”

Eventually, Brown sent messages to the woman he believed was his mom.She ignored them. He then mailed letters to her, to Michael and to Michael’s former workplace, the syndicated show Live!.

After getting no replies, Brown wrote to Strahan’s parents in Texas. At that point, a New York City private detective contacted him on Strahan’s behalf.

According to Brown, he and his parents met the P.I. at a Manhattan diner, and Strahan later agreed to a paternity test — but only at a Park Avenue lab of his choosing.

Convinced the deck was stacked against him, Brown refused.

“I felt like if Mike wanted the results to go a certain way, that was the way they would go. I thought Mike might reach out after that. He never did,” said Brown.

But Strahan’s reps insist Brown’s claims are part of a “continuing” shakedown, and that it was Brown who walked out on the DNA test.

Strahan has four children from two previous marriages — Tanita, 24, andMichael Jr., 22, with ex Wanda Hutchins, and 11-year-old twins Sophia and Isabella with his ex Jean.

As Radar reported, Strahan’s now living in a trial marriage with strip-club squeeze Kayla Quick, 27.

And Brown continues to seek the truth.

“My adoptive parents are the best, but I want to look my father in the eye,” he said. “I don’t want anything. I just want to know who my family is. Do I have brothers and sisters? Everyone deserves that.”