"Duck Dynasty" star John Luke Robertson is grateful that his fiancée Mary Kate keeps him close to Jesus.

In an interview with Us Weekly, John Luke shared the history of their love and how Jesus is the centre of their relationship.

The conservative Christians met four years ago at a Christian summer camp, he told the website. He also said that they started connecting in high school during chemistry class. "There was some chemistry," he quipped.

The 19-year-old added that it took him about a year just to win Mary Kate's heart. "I had tried to date her before, and she kept turning me down! I just kept at it and she finally said yes!"

Aside from the "chemistry", John Luke said his fiancée has always been a great listener. Being in love, she would laugh at his jokes and most importantly, "she never gave me the time of day until I started talking about Jesus," he said.

He added that this made him realise that "she was a good one", although it didn't escape his attention that she happens to be quite pretty too.

"She would help me grow in my faith," he said. "And she was pretty good looking!"

The couple got engaged on October 11 and Mary Kate, 18, has also spoken about their common passion for their Christian values. "I had always prayed God would bring a Christian boy into my life."

"When John Luke came into the picture, I figured God had placed him there. He's an awesome man of God. He's really funny, you never know what's going to happen with him," she said.

She also did not take away the fact that her fiancée is "pretty cute", an added bonus.

Meanwhile, John Luke's sister, "Dancing With the Stars" contestant Sadie Robertson is supportive of the union. In an interview with E! News, she said that she is excited to have her best friend marry her brother.

"I knew it was going to happen. Like I said, she's my best friend, and she's been my best friend since before they started dating, and I had knew it was coming, and I was super-excited!" Sadie said.