Disturbing marriage practices. Eskel Grant opens up about the religious sect his family belongs to in Escaping Polygamy‘s Sunday, August 7, episode, as seen in Us Weekly‘s exclusive sneak peek.

The A&E unscripted series’ preview clip shows Grant revealing that his father has three wives, including one who is a blood relative. Their family is part of the polygamist Salt Lake City–based Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS).

“I always thought that was really strange and really weird that he married his half-sister,” Grant says of his dad.

He goes on to talk about the difficulty of dating within the religious group, explaining, “My dad says that you have to have multiple wives to go to the celestial kingdom, but when you’re a guy in my church, it’s just extremely rare to marry a girl the same age as you. Usual age difference from a married couple is seven years, so when I’m 21, I can marry girls as young as 14.”

Later in the footage, an anonymous whistleblower says that the church encourages incest: “If you’re going to get married in the Order, your choices are basically your family.”

A previously released clip from this season showed former FLDS member Jennifer, 18, defending having fallen in love with her cousin, 30. Another preview snippet featured Andrea revealing that her dad has made her eat her own vomit.

Watch the clip in the video above to see images of Grant’s dad with his various wives. Escaping Polygamy airs on A&E Sundays at 10 p.m. ET.