The most beautiful relation in India as well as in the World is of brother and sister. They fight, they love and they tease but still stay together. This is a beautiful bond, when young they love each other as siblings and when they grow up they become friends. This bond is incomparable with any other relation.
So to celebrate this bond we have a beautiful festival of Rakshabandan in India and some other Asian countries. Rakhi is celebrated since ancient era; many mythological stories are associated with this festival.