'The Bachelor': Sean and Catherine Lowe on the Secret to Their Successful Marriage (Exclusive)

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The fan-favorite couple revisit their 'Bachelor' journey with ET.

Sean and Catherine Lowe are one Bachelor couple who made it. While a handful of other Bachelors have ended up with another woman from their season, after 18 years and 24 seasons, Sean remains the only male lead to marry his final pick. As he told ET's Lauren Zima on Monday, there's a reason for that -- or "two or three."

"One, my wife selflessly decided to move -- leave her family, her friends, her job, her life as she knew it in Seattle to come live in Dallas," Sean explained. "Every season, the people that end up together usually don't live in the same city, so somebody has to make that sacrifice. That's extremely hard, so I give Catherine all the credit in the world for that." 

Next, Sean thinks their Christian faith "has a lot to do with" their lasting marriage. "Just the commitment, 'Hey we're going to start our marriage on this foundation of God and grow together, and commit to grow together no matter what. I think that's helped tremendously," he said. 

"And then, I found my best friend. On the show, we would say, 'Wouldn't it be nice if we could just put sweatpants on and lay on the couch and watch Netflix?' That is who I found, as opposed to just picking someone just purely based something superficial," Sean added. "So, I think those are three pretty good reasons why it's been able to work for us." 

Sean and Catherine's love story was revisited on Monday's premiere of The Bachelor: The Greatest Seasons -- Ever! The three-hour episode showed the pair's road to engagement... as well as the drama Sean went through to find his true love. 

"It's kind of funny, I thought we would've ridden into the sunset a long time ago and people would've forgotten about us," said Sean, whose season aired in 2013. He married Catherine in a televised wedding the following year. "So, to relive it and rehash everything and the spotlight being on us momentarily, it's kind of a blast from the past." 

"It's a little weird to watch your husband kiss other people," Catherine confessed with a laugh. "But knowing that it was kind of who we were at the time, just bringing that into perspective and knowing what we have now, it's fine. And I just love looking at the memories that I had with the girls and the fun times that we had." 

Sean and Catherine are now parents of three: 3-year-old Samuel, 2-year-old Isaiah and 5-month-old Mia. Sean is hoping his sons have no interest in watching his Bachelor journey, but worries Mia might get curious when she's older. "I'll let her watch it with Mom and I'll let Mom answer all the tough questions," he joked. 

Catherine's got it covered. "I had a videographer edit [the season], so it's pretty much just us. So, I think that would be an easier transition for them to watch, so they're not like, 'Why is Daddy kissing all these other women?'" she revealed. "It'll just be like, 'Oh, that's sweet. That's the first time you saw her.'" 

Fans watching Monday night's episode of The Bachelor: The Greatest Seasons -- Ever! got the full story, and including the saga that was Tierra. The Bachelor contestant was a major source of drama in the house... and at the hospital. 

"I believed [she really fell down the stairs]," Sean said of Tierra's fall during the season that had her briefly put in a neck brace. 

"We think she fell up the stairs," Catherine confessed. The mom of three does believe, however, that Tierra really got hypothermia after diving into freezing cold water on one of their group dates. "She looked really blue. I was there. She came back to the hotel and she looked like she was not faking it." 

"She looked blue, but I think she was nursing it a little longer than she probably should have," Sean guessed. 

"Maybe... but I think she was actually in pain," Catherine chimed in. 

Catherine managed to stay out of the drama in the house on The Bachelor -- but witnessed a lot of the Tierra show. "She's not a bad person. I just think that it didn't work out for her," she offered. 

"Bless her heart, she went on that show and I don't think she was adequately prepared for that environment. Just being amongst all the other women and she just emotionally could not handle it. I know she came across pretty bad on the show. I think she's very lucky it was 2013, because today I think she would get ripped to shreds [on social media]," Sean said. "I hope she's doing well. Hopefully she left all that behind and she's able to start over fresh."

Several of Sean's other exes were featured on Monday night's episodes, with many now happily married with kids. As for Sean and Catherine's growing family, the couple admitted that fans could see it expand even more. 

"Yeah, we need that title," Sean cracked of beating fellow Bachelor fan-favorite couple Tanner Tolbert and Jade Roper with highest number of kids. "So as soon as I can get [Mia] to take a nap, we're going to work on No. 4." 

The Bachelor: The Greatest Seasons -- Ever! airs Mondays at 8 p.m. ET/PT on ABC. See more from Sean and Catherine's interview on Tuesday's ET.