Well the possibilities are that you have been frozen for 200 years, you were injured in the blast and were put into stasis and forgotten, you died and the vault made an android version of you, you are clone, everyone died in stasis but you.
Also not a fan of family NPCs. For example in FO3 you only see dad in the intro for like 5 minutes then he bails. I need to have some sort of longevity to care about someone.