Controversial American reality TV series 'Sister Wives', which follows the polygamous life of Kody Brown and his "extended" family, is expected to welcome its latest addition and supposedly its newest cast member in the show's forthcoming season.

Robyn, the fourth of Brown's wives, has been confirmed pregnant and is expected to be delivering the latest Brown by the show's 6th season. Although the announcement has not been officially released yet, patriarch Brown has reportedly made unofficial confirmation of the news on social media's Twitter.

The news is expected to cause tension in the family as Brown's legal wife, Meri, has always been uneasy about her husband's extramarital activities.

The youngest of Brown's four wives, Robyn, was first introduced to him in 2010 by his first wife, Meri. Robyn's latest child will be the 18th member of Kody's family.

Although Brown and Meri have been married for nearly 24 years and are parents to 22-year-old daughter Mariah, Meri had become infertile shortly after she delivered their firstborn.

Apart from Meri and Robyn, Kody has two other wives: Janelle, his second wife with whom he has 6 children, and Christine, his third wife with whom he fathered 6 more children.

Following Robyn's big pregnancy disclosure is Meri's hint on an equally-immense revelation. Recent reports claim that Meri might have been hinting on leaving the Brown family for good. It can be recalled that Brown's legal wife has constantly expressed disapproval of their family's polygamist arrangement, although she herself was raised in a family of the same disposition.

The 'Sister Wives' is expected to have their reunion on July 27th.