The deeply religious family patriarch married his wife Kay, known as Miss Kay, in 1966

The Duck Dynasty is bigger than the family thought.

Phil Robertson and his children Al, Jase, Jep and Willie revealed during the Unashamed podcast on Thursday that the family recently discovered the deeply religious patriarch has an adult daughter.

During the podcast, Al explained that he received a letter from a woman named Phyllis, who was 45 and claiming to be his sister.

"So basically, it was from a woman who said that by a DNA search, she thinks that dad might be her dad," Al said, adding that he had "dismissed" the letter at first because the woman's birthday was after the time Phil had become a Christian in the 1970s.

Phil Robertson
Phil Robertson
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Phil has previously admitted to being a philanderer prior to finding Jesus, however, it appears his daughter was conceived just before he devoted himself to the church.

Phil married his wife Kay, known as Miss Kay, in 1966. The pair remain married.

"Well once we get into that and start looking at it a little more deeply, I'm like, 'Oh woah, woah... there might be something to this,'" Al said.

Al continued to say that he didn't want to bring up Phyllis' letter right away to Phil in case it wasn't true.

"We both concluded, this is not one of those frivolous things we've got," added Jase, who also received a letter from the woman.

"We had to pursue it," Al agreed.

Phil and his family
| Credit: A&E

"I started thinking, there's a 45-year-old woman out there who doesn't know who her dad is, and she's looking," Al said. "And I thought, even if it's not dad, she needs to know it's not dad."

Al finally approached his parents, and Phil agreed to take a DNA test — which ended up being a "99.9 percent match."

Phil interjected to say that when he got the call of his parentage, he said, "bring her on down" so they could meet.

Duck Dynasty
Willie Robertson, Korie Robertson, Phil Robertson, Miss Kay Robertson and Si Robertson
| Credit: Dimitrios Kambouris/Getty Images

"We know that in all things — in all things — even sin, God works for the good of those who love him who have been called according to his purpose," Phil said, paraphrasing Romans 8:28 from the Bible.

Phil said that the family has already met Phyllis and that the Duck Dynasty audience can expect to meet her soon on an upcoming episode of the podcast.

"It's a pretty cool explanation of redemption, reconciliation, love," the Robertson patriarch said. "As it turns out, 45 years, you have a daughter that you don't know about, and she has a father she doesn't know about. 45 years that doesn't sound like very long but you say, that's a while. So finally, after all those years, we come together."

"It was super awesome, I was so excited," Jep said of the news, adding that he always wished he had a sister growing up in a family of boys. "It was like a dream come true."