How genetically similar are brothers and sisters?

“Between two non-identical siblings or parents and children, the proportion of shared genetic variants is 50 per cent,” explains Alun Williams, head of the Sports Genomics Lab at Manchester Metropolitan University.

Only Ffion and Megan grew up in a cycling household from birth. Were they destined to follow in the wheeltracks of their siblings?

“To have the potential to do the same thing at a high level, there’s between a 60 and 70 per cent inherited component,” Williams continues. “Environment, family and role models are also important, but siblings do share much of the same biological potential.”