Kody Brown's brood is about to get a lot bigger.

The star of TLC's Sister Wives and his fourth wife, Robyn, are expecting their first child, a rep for the network confirms to UsMagazine.com.

The baby, due in mid-October, will be the 17th child for the Brown family, which also includes Kody's other wives Janelle, Christine, Meri and their kids.

Robyn, 31, who has three children from a previous marriage, tied the knot with fundamentalist Mormon Kody, 43, on the first season finale of Sister Wives.

Ad salesman Kody admits that a criminal investigation into their lifestyle was a contributing factor, among many others, in his growing family's January relocation from Lehi, Utah to Las Vegas.

"We didn't want this thing hanging over us," Kody told ABC News in March. "We went to Vegas with hopes of having a good life, preserving the family. ... We never did anything here at all to be rebellious, to challenge the statutes of the law, or anything like that."

Adds Robyn: "We still have our family. That's all it boils down to."