When Rosemary Redmon died she had one wish: for her granddaughter to marry her husband.

I've fallen down The Real Housewives rabbit hole; and recently, I started watching The Real Housewives of Salt Lake City.

There were two things that intrigued me about the series: most of the cast are Mormons, and one is married to her step-grandfather. Yep. 

Watch the trailer for the Real Housewives of Salt Lake City Season 5 here. Post continues below.

Mary Cosby, who has returned to the full time RHOSLC cast in Season 5, is one of the few women on the show who is not part of the Mormon faith. Instead, she's described as a "Pentecostal First Lady".

In 1997, Mary's grandmother Rosemary passed away, leaving her millions of dollars, businesses and her family's Pentecostal mega church. 

But in order to receive her inheritance, she would have to marry her step-grandfather.

Mary's grandmother had been married to Bishop Robert C. Cosby Sr. for 22 years.

He was significantly younger than her and was her second husband (making him Mary's step-grandfather).

Image: Bravo.

Mary married him when she was in her early 20s, and Robert was in his 40s.

"My grandmother told me, for herself, that she wanted me to take her place," she said on the reality TV show before explaining Rosemary's reasoning. 

"Basically, Robert Sr. was 20 years younger than my grandmother. My grandmother felt like she robbed his youth. 

"So she said, 'If something ever happens, I want you to marry one of my girls, because I know that they will be loyal to you and treat you good like you treated me.'"

Mary admitted that she didn't want to go ahead with the 'arranged marriage'.

"I did marry him. I didn't want to. That's weird to me," she said.

"But [my grandmother] really did want me to, so I obeyed her. 

"I trusted every word. If she managed to bring this church this far, then she had to be right. And look at my life."

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Mary said she sat on the idea before going ahead with it.

"It took us two years to actually marry," she continued. "I had to be certain. I started to pray myself, I started to seek high help myself. When I did that, I felt peace with it, so I married him. I chose what the man upstairs told me to do."

Not only did Mary used to call her husband "Grandpa", but she also has a child with him: a teenage son named Robert Jr.

Despite the judgement, Mary says they are happy.

"You can't say or do anything to take happiness away from me," she said during the show's reunion. 

"It's hard to get. If you can find that in a man, it doesn't matter where he came from."

Robert remains the pastor at Faith Temple, and Mary runs services as their First Lady.

Mary Cosby has returned to the Real Housewives franchise. Image: Hayu.

In the first trailer for the fifth season of The Real Housewives of Salt Lake City, which premieres in September, Mary was seen having a heart-to-heart with her son, Robert Jr. 

"I felt like a stain," he says, to which a tearful Mary replys, "You have to know I love you more than anything."

The raw moment is sure to be one of the most important plot points, as Mary keeps her cards somewhat close to her chest on the show.

You can watch all four seasons of The Real Housewives of Salt Lake City (and every other Real Housewives franchise) on Hayu.

Feature image: Bravo.