Surya Dev aur unki patni Sangya (Chhaaya) ke do santaanen thin — putra Yamraj aur putri Yamuna. Bhai-behan donon mein atyant gehra sneh tha. Yamuna ka hriday komal aur prem se bhara tha, jabki Yamraj ko praaniyon ke praan harne ka kathin daayitva nibhaana padta tha.
Yamuna apne bhai Yamraj se baar-baar aagrah karti rehti — "Bhaiya, ek baar mere ghar bhojan par padhaaro, main apne haathon se aapko bhojan karaaungi." Par apne kaaryon mein atyant vyast Yamraj har baar baat taal jaate aur "phir kabhi" kehkar reh jaate. Yun hi bahut samay beet gaya.
Ek baar Kartik maas ke Shukla paksha ki Dwitiya ke din Yamuna ne phir se prem-bhara nimantran bhej kar bhai ko bulaaya. Is baar Yamraj apni behan ke is achal sneh aur aagrah ko taal na sake. Raaste mein unhone narak ke jeevon ko mukt karte hue, aanand ke saath behan ke ghar ki ore prasthaan kiya.
Bhai ko apne dwaar par dekhkar Yamuna ki khushi ka thikaana na raha. Usne snaan-dhyaan karke, ghar ko saja kar, bhai ka tilak kiya, aarti utaari, mistha-pakwaan banaakar prem se bhojan karaaya aur uske deerghaayu va kalyaan ki kaamna ki. Behan ke is nishkaam prem aur aadar-satkaar se Yamraj atyant prasann hue.
Prasann hokar Yamraj ne Yamuna se var maangne ko kaha. Yamuna ne kaha — "He bhai, mujhe yeh vardaan dijiye ki jo bhai is din apni behan ke ghar jaakar, sneh se tilak karwaaye aur uske haath ka bhojan kare, use aapka (Yam ka) bhay na rahe aur use akaal-mrityu na aaye." Yamraj ne "tathaastu" kaha aur yeh bhi var diya ki is din jo bhai-behan Yamuna mein snaan karenge, ve Yam-yaatna se mukt rahenge. Tabse Bhai Dooj (Yam Dwitiya) ka pavitra parv manaaya jaata hai.
Seekh: Bhai Dooj bhai-behan ke pavitra aur nishkaam prem ka prateek hai. Behnein is din bhaaiyon ki deerghaayu, aarogya aur unnati ki kaamna karti hain, aur bhai unki raksha ka vachan dete hain — sneh aur kartavya ka yeh bandhan sabse pavitra hai.