So this chapter is gonna be a introduction as many of you had some confusions.
The Agarwals - They are a wizarding family and they live in India and they were keeping care of Darry .
Darry - During the night of that Halloween he got two scars because he was hit by the killing curse twice by Voldy and he was cursed by Dumbledore so that he doesn't remember this until he gets his Hogwarts letter.
Sam - He is basically Darry's best friend from the first year of muggle school .
As for why I chose India was because it might bring a new light in the story and he would be away from Voldy for the first few years of his life and it would be very difficult for Darry to remember everything on his own.
If you have any doubt you can ask me and I will answer it.