Technicially it would be Gaara(even though Gaara is not a blood sibling of Naruto's) because they went through the same hardships as childhood, understand each other completely, and because they both have the tailed beasts inside them(which might make them blood relatives).
No not that i am aware of, naruto does not have a sibling
He has no known siblings
Yes, Hinata and Naruto have two children together: Boruto and Himawari. Boruto is the older sibling and a main character in the "Boruto: Naruto Next Generations" series.
No Harry Potter doesn't have any sibling's.
There is naruto pedia and naruto arena
no
I have a big sister
No, there won't be any more Naruto after Naruto Shippuden.
Yes
no their is no cheats in naruto-arena.
right now,no
Most costumes are timeless. A witch or ghost costume can always be used by a younger sibling.