I think the blonde hair dude is mc not his bro if you mean the guy in ch1 and the blonde guy probably didn’t die? I am not sure either but likely after recovering mc got found out by the corps sent from the city to find him.
Then he awakens fully thus becoming light haired. It said in the story partially awakened people still keep their original hair color and become silver haired means you awakened fully.
As for the rape I really don’t know the story didn’t explain, they will likely explain as the story progresses. Maybe it’s guide/esper combo trope? Ehhh probably not. Maybe to extract power or oppress/control/experiment on him? Or just a corrupt rich people thing to rape a good looking youngling, female or male. Meh
They didn’t make it explicit this is just my understanding of the story TvT

So his little bro is still alive? And interesting morally gray from his pov
I wonder what will happen next
Now I’m sad I discovered this too early
But a series I’m actually looking forward to!!