Brother

So what, you grew a little, maybe you will reach a normal height! Her 6'3" tall brother didn't lose a shred of confidence, but his sister soon challenged him:

Let's go back to back

Ok, that was pretty obvious, he still was 1 foot taller.

Now let me armwrestle you!

Now for some reason her brother lost, besides putting all his strength! He looked on terror, to a growing and stronger little sister

After the tiresome exercise, hes mind was bugging something

And he decided to measure his sister again

How tall was she now ?