Shortly after her high school graduation Kelly tells her father that if he didn't want her to tell her mother that he had gotten her pregnant that he would have to continue to have sex with her and to give her many children. Kelly is one of the youngest of a huge family and she knows her father can give her many children.
The father agrees to this but only if she's willing to let some of her brother-in-laws and or other male relatives have chances of being the father of several of her babies. She agrees. She may end up having many children. Possibly more than the amount of siblings she has.