Averages can be misleading

According to a BBC News story, a researcher in Britain claims that having an older sibling, particularly a brother, can stunt your growth, and that children from larger families (4 or more children) tend to be shorter than average. From my own experience, I beg leave to doubt this. I am the oldest of five, and 6ft 3in. My next two brothers are also over 6 feet tall, while my youngest brother is 6ft 7in. My sister, the youngest of us, is 5ft 10in. Obviously we are all far above average!