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In his new autobiography " An American Son," which goes on sale Tuesday, Florida Sen. Marco Rubio, writes about his Christian faith and a fact that is not widely known - as a child he and his cousins were baptized in the Mormon church.

"We were in the Mormon church I guess by the time I turned eight," he told ABC News' David Muir.

Rubio, 41, was living with his family in Las Vegas at the time and took a liking to the musical group the Osmonds.

"The Osmonds were pretty popular back then, especially among Mormons, but I think among a lot of Americans. But we had a group called the Sunshine Cousins," Rubio said. "It was me, my sister and my cousin and we, we would lip sync basically."

Click here to hear what Sen. Rubio thinks about President Obama's immigration policy.

Rubio's father was "skeptical about the church's teachings," and by the time the family relocated back to Miami, they also rejoined the Catholic church. Rubio said he was 12 or 13 when his family moved back to the East Coast.

"We did our first communion in Las Vegas before moving back to Miami," Rubio said. "I know people find it interesting, it was a period in our lives and our family in Las Vegas, we have a large extended family of cousins, second cousins and others who are still part of the LDS church."

The Miami-born Rubio, is the son of Cuban immigrants, a point of pride for the politician, who has used his family's story as a selling point on the stump. However, his family narrative came under scrutiny after the Washington Post revealed that Rubio's parents did not flee Castro's Cuba as Rubio had said, but instead left Cuba before Castro took power. Rubio insists that while the date may be different, it doesn't change the lessons that can be learned from their struggle.

"I regret not having the date right because I could have avoided that distraction, but it was a blessing because it forced me to go back and say 'OK, let me get all the facts and put it in order.' And what I found is that my parents are even more interesting than I suspected," Rubio told Muir. "My parents were born, lived and loved their country that they are no longer able to be a part of or go back to and that they were permanently separated from and because of that they were grateful to the United States, they valued freedom and liberty and they instilled that in us at a very young age."

Those are values that he said he and his wife, Jeanette, are now trying to pass on to their four children.

The couple met through mutual friends and dated for seven years before getting married. Rubio, a Miami Dolphins fan since childhood who always dreamed of playing in the NFL, said he likes to joke that "I can tell my kids that one of their two parents used to work on an NFL field, but it was not their dad."

"I was a Dolphin cheerleader for a year. I did it when I was young. I was not married," Jeanette Rubio said. "It was a great experience. I was a cheerleader in high school, my sister was a cheerleader for the team as well. I took the opportunity, I made it and I had a great time."

Rubio says one of the hardest parts of his job as a senator is trying to find an appropriate work-family balance. Even when he's not in the office, he's still on the clock.

"When my dad came home, he was home. … We have family members that have that ability, too," he said. "For me there is a certain - not envy, but longing for that when you punch the clock and you're done, you're done. … Sometimes it is not possible in this career. You come home, but your emails are still coming."

Jeanette Rubio described her husband as "funny" and "committed." Despite his busy schedule, she said, he always tries to make time for family.

"He's at an event and he finds out the kids have something that is important, he always tries to find out how to get from point A to point B. Even as a husband, whenever I need him, he'll move whatever he has to be there," she said. "I hope one day [the kids] will decide to go out and make a difference and emulate their dad in some way."

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