That Time Mario Rubio Was Partially Responsible for Little Brother Marco's Birth

— MYRTLE BEACH, S.C.. -- Mario Rubio doesn’t like to brag, but he’s one of the reasons his brother, presidential candidate Marco Rubio, was born.

“Well, my mother called -- she couldn’t get a hold of my father and so I took her to the hospital to deliver him,” he told ABC News during a recent visit to a South Carolina field office.

At 21, he was old enough to be Marco’s father -- and that’s exactly who hospital staff thought he was.

“They wanted me to sign some paperwork and I said, ‘I can’t sign it. I’ve got to wait for my father,’” he recalled, eyebrows raised. “They said ‘You’re old enough to have a child, and you have to wait for your father?’ I said, ‘No, that’s my mother!’”

Now, the trim 65-year-old, who left Cuba with his parents as a boy and went on to become a Green Beret, is helping his brother in a different way: speaking to veterans across military-minded South Carolina. The state boasts several active military bases and training centers, making veterans affairs and foreign policy a constant talking point on the campaign trail.

In December, Marco Rubio, 44, described his brother's challenges as he left the Army Special Forces.

“He was hit in the mouth while in jump school,” the Florida senator said. “Today, he needs more orthodontic work as a result of his injury, but the VA won’t cover it. … My brother, like all of our veterans, deserves better. When I am president, they will have better.”

Republican presidential candidates have received plenty of figurative socks to the jaw in the lead-up to the South Carolina primary, considered by locals to be one of the most contentious in recent memory. The latest controversy to make the “dirty trick” playbook: an apparently digitally altered image of Rubio, appearing on a website paid for by the Ted Cruz campaign, that portrays him shaking hands with President Obama.

The Rubio campaign quickly said he doesn't own the tie or watch featured in the photo, and produced a stock image virtually identical to the one in dispute, featuring someone else's head. Cruz spokesman Rick Tyler dismissed the complaints as petty.

Mario said he’s not worried about his brother, who he says grew up playing dodgeball in his backyard.

“It’s harder, I think, on my mom than it is on me,” he said. “I understand how they do this stuff in politics. Mom doesn’t like somebody talking bad about her little boy and so those kind of things get to her a little bit. But I’m used to seeing those things. I’m just very proud of him.”

Mario has a few more battle scars of his own: He injured his left knee in high school, which derailed a potential college football scholarship.

“The Army took me,” he said. “But then I hurt my right knee in the Army! But the left knee is fine.”

Asked whether his younger brother’s tales about him as a star quarterback were exaggerated, he kept a straight face.

“Well, let me put it to you this way,” he said. “On April 16th, I’m being inducted into the High School [Athletic] Hall of Fame in Florida.”

But he doesn’t like to brag.