No one can predict with any degree of certainty the physical attributes of an athlete. Lineage can provide a glimpse of certain characteristics like height and body structure, of course. But there are more important factors to focus on in the development of a young athlete.
Yes, contact sports are dangerous. Competitive soccer, volleyball, swimming, gymnastics, baseball, etc. are not without risk. But stop and think about the risk of your kid not getting to participate in a team sport.
As someone who has avidly watched and followed football for years, I failed to grasp the severity of the many injuries. I ignored the commentators and analysts who believed that football needed to get safer.