In this book, Luke Garner is a boy who has two older brothers.  This is a problem because in their society, third children are forbidden.  So Luke has to hide all the time.  Eventually, in the book, he meets Jen (Jennifer Rose Talbot).  Jen is also a third child.  Over the course of the book, she teaches him a great deal about their society.  She is eventually killed at a protest rally.

Jen's brothers (actually they are step-brothers from her mom's first marriage) are nicknamed Bull and Brawn.  Their real names are Buellton and Brownley.