How, indeed. This is the question raised by JJ in the season finale of Big Love. Allow me to explain.
One of the show's many plotpoints this season was this: Nicki is having trouble getting pregnant, so she's been seeing this Mormon doctor for special treatments. The doctor finally tells Nicki her eggs are no good, she's infertile. Nicki gets depressed. Then Nicki's ex JJ finds out, and starts scheming. By the way, there's a subplot about how there's been a spike in deformed babies coming out of Juniper Creek and people are accusing the Mormons of inbreeding.
Anywho. JJ somehow gets Nicki's doctor to try to implant an embryo in Nicki. What kind of embryo, you ask? One that comes from the union of his sperm and Cara Lynn's egg. Who's Cara Lynn, you ask? His and Nicki's DAUGHTER.
Thankfully, Nicki's mom storms into the doctor's office just in time to stop him from implanting the embryo in a drugged-up, semi-concious Nicki. What is Nicki's mom's involvement, you ask? Well, she happens to be pregnant. With a JJ/Wanda embryo. But who's Wanda? JJ's SISTER.
Turns out JJ has been running a no-sex incest clinic, which explains all the deformed babies. Why is JJ running a no-sex incest clinic? I don't know, and I didn't feel inclined to rewatch the episode to find out. Anyway, the WHY here is not so important as the WHAT. And that WHAT is something I'd like to forget about as soon as I finish writing this post.
Oh, and the other thing that happened in the finale was Bill finally came out as a polygamist. He had just won a seat in the state senate, and during his speech, decided to introduce himself and his three wives. I love that after he introduced his second wife, some random lady in the crowd yelled out, "How many ya got???"
All in all, it was a bizarre, sickening, yet satisfying way to end the season. What will happen to the Henricksons now that they're public? Will Bill keep his seat? Will Nicki get pregnant? Will Adaleen (Nicki's mom) give birth to her daughter/granddaughter? We'll find out next season!