Sure there are exceptions to the rules. With new mutations, someone in the family carrieing a taller height gene, that has been suppressed by unknown reasons. Playing around with growth hormone (it's been used in sports for ages now).
There is a simple formulae for calculating heigh of a baby. Dad's height + mom's height +-13 (+ if a boy, - if a girl) / 2, with girls the range is +-8, with boys +-9. Obviously there are a lot of variables that can influence height in fetus stage or later in life (like mom's diabetes, excess insulin in fetus stage, tumors, bad habits like alcohol in the early age etc).
But we are drifting away from the topic again...