On the last day of the five day long Diwali festival, the special bond between brother and sister is celebrated as Bhai Dooj or Yama Dwitiya.
As this festival falls on the second day of Shukla Paksha of the Hindu month Kartika and on this day sisters pray for the long life of their brothers (bhai or bhaiyya) [and the brothers give gifts to their sisters :P] it is called Bhai Dooj.
There are two legends associated with this festival.
1) In continuation with the legend of Narakasur, it is believed that after killing Narakasur, Lord Krishna went to meet his sister Subhadra. Subhadra welcomed him and showered him with love. Some say this is the origin of Bhai Dooj.
2) In another version, on this day Yamaraj, the God of death, went to visit his sister’s house after a long period of separation. His sister, Yami was very happy to see him and welcomed him warmly. He was so pleased with his sister’s reception, he proclaimed that every year, on the dooj day, if a sister puts a tilak on her brother’s forehead, then no one can harm her brother. Therefore this festival is also called by the name Yama Dwitiya.
Cheers to the bond of love between all the brothers and sisters in the world 🙂