Achilles was a Greek hero from the infamous Trojan War, who was said to be invulnerable everywhere on his body, except for his heel; hence the world-renowned saying of Achilles Heel, which has been used to point out flaws or weaknesses for hundreds of years. If you're familiar with the story of Achilles, you know that he died in the Trojan War, but what happened next?
Did you know that Achilles had a son? His name was Neoptolemus(or Pyrrhus to some). Neoptolemus had three sons, some people even say four: Molossus, Pielus, Peragamus and Amphialus, which of the four may or may not be his son is unclear… but that's not the point! These sons grew to men and had more sons, and throughout the ages the Achilles name spreads like wildfire. However, in all of this time the blood line loses purity and fades into nothingness, right?
But we all know that certain genes can lay dormant for years. What if it suddenly reactivated? What if it happened in our time? It could happen at birth and everyone knows something is different, or it can have a trigger, like puberty or adulthood or something. Could you imagine walking down the street, just like any other day, only to discover by chance that you're invulnerable?!
Well… maybe not invulnerable. If you look back at the Greek legend, Achilles was invulnerable in the sense that no one could seem to get a hit on him, like he had superhuman reflexes! Spidey-senses moment!
There are endless possibilities that could go with a story based on a descendant of Achilles. It worked with Percy Jackson, didn't it?
If you like this idea and want to get started on some research, here's a few Wikipedia links that could prove to useful, or at least get you started: