The "Sister Wives" family will soon have a new member.

The family confirmed that Kody Brown's fourth wife Robyn is pregnant with their second child together, which means that the Brown household will have 18 children all in all. 

"We are so happy to announce an eagerly expected new member of the Brown family!" the Browns publicly announced through PEOPLE. 

Kody and Robyn got legally married in December 2014 after he and his first wife Meri Barber divorced in September on the same year. They have been together through a spiritual marriage since May 2010. Aside from Robyn and Meri, Kody has two other spiritual wives, Janelle and Christine. 

The Browns are members of the Apostolic United Brethren, a Mormon fundamentalist church that allows polygamist relationships. The AUB is a faction of the Latter Day Saints movement. 

Kody currently has 17 children with his four wives. Meri gave birth to their only daughter Mariah in 1995, while Janelle bore six children, namely Logan (1994), Madison (1995), Hunter (1997), Garrison (1998), Gabriel (2001), and Savannah (2004). 

Christine also gave Kody six children, including Aspyn (1995), Mykelti (1996), Paedon (1998), Gwendlyn (2001), Ysabel (2003), and Truly (2010). Solomon, Robyn's first child with Kody, was born in 2011, but the Brown patriarch legally adopted her three older children from a past relationship when they got legally married. The kids are Dayton (2000), Aurora (2002), and Breanna (2005). 

Kody will have a total of 18 children after Robyn gives birth to their second child in January 2016. 

The Browns became famous since TLC aired their show "Sister Wives," featuring their polygamous family. While a lot of people were accusing Kody of breaking the law by keeping more than one wife, the Brown patriarch constantly explained their chosen lifestyle through their show. 

"While we know that many people do not approve of plural families, it is our family and based on our religious beliefs," Kody said after a Utah judge struck down a portion of the state's anti-polygamy law that bans polygamous households like theirs. "Just as we respect the personal and religious choices of other families, we hope that in time all of our neighbors and fellow citizens will come to respect our own choices as part of this wonderful country of different faiths and beliefs." 

TLC has yet to announce the premiere date of "Sister Wives" season 6.