Lighting and Shadow ( A Fanfic of Batman's daughter and Flashes Daughter!)

What would happen if Batman had a daughter before the Robins or Batgirls came around. What if Flash had a daughter two and her and Batmans daughter became BFFS. Polar opposite, Best Friends who help each other in the world. But, what happens when these two become super HEROS. What if they leave their homes? What if they never come back? Thy become
Lighting
And
Shadow