According to mythology, the god of death is Yamraj, but do you know that Yamraj also has a sister? His sister's name is Yami or Kanalidi. Yami is the daughter of Suryadev and is the sister of Shani Dev. Yami flows on earth in the form of Yamuna River and she has the status of Goddess in mythology.
It is said that Yamuna loved Lord Vishnu very much, so he did penance to Lord Vishnu. Lord Vishnu gave him a boon that when he comes in the Dwapar Yuga, he will marry him. In the Dwapar Yuga, when Shri Krishna was born and he was crossing the Yamuna river sitting in a basket on Vasudev's head, then Yamuna touched his feet. In childhood, Shri Krishna used to play on the banks of Yamuna.
Later, Yamuna river lived in Khandava forest as Kalindi. The city of Pandavas was Indraprastha near this forest. One day when Shri Krishna and Arjun were roaming in the forest, they felt thirsty and felt coolness. On going a little distance, he met a woman as Yamuna ji.
Shri Krishna introduced himself to Yamuna ji, and reminded him of the boon of marriage. Then Yamuna and Shri Krishna were married in the same forest. Shri Krishna gave Yamuna ji a boon to be revered, and after that the Yamuna got absorbed in her stream. We are not giving us here, but is based on religious beliefs.