Varuni

"Shesha had a wife, Goddess Varuni (she is goddess of sky and intoxicating drinks ).She was daughter of Varuna and churned out during samundra manthan. She is sister of lakshmi as lakshmi too came out of samundra manthan .Then Ananta claimed her...it is said that once Varuni and Shesha were enjoying each other's company and then a sage Dandachi came with a imp msg of God but Varuni and shesha completely ignored him.Sage was so furious at them that he cursed them that they shall bear pangs of separation.Will be forced to observe celibacy despite being wife and husband. Lord Shesha and Varuni asked for forgiveness. Shesha said," they are nagas... serpent are by nature like this plz forgive." But sage curse couldnt be reversed . When sage went to Vishnu ji, he said..." dont worry this is for the good of the mother earth...soon after this lord shesha will do penance and will gain my aquaintance and then he and varuni will be born as my brother and sister in law and with the help of this curse meghnanad will be killed"...so in the next birth lord shesha and varuni took birth as lakshman and urmila

Also
http://www.sacred-texts.com/hin/hmvp/hmvp27.htm