In the Mahabharata, Kripi is the wife of Drona and sister of Kripa or Kripacharya. Story of the birth of Kripi is found in the Agni Purana. She was the daughter of Rishi Sharadvan and celestial nymph Janapadi. Although Sharadvan was born in the lineage of saints, he was more interested in Dhanurveda (science of archery). To show his deep interest some scriptures states that he was born with bow and arrow.
An expert archer from a young age, Sharadvan did intense penance in the forest to learn all the nuisances of archery. Keeping his bow and arrow nearby he performed Tapas to get blessings from the Trimurtis.
As the intensity of the penance of Sharadvan increased, Indra, King of Devas, felt threatened. He saw Sharadvan as a potential threat to his throne and status.
To break the penance, Indra deputed celestial nymph Janapadi. She enticed Sharadvan in numerous ways but found on success. Finally she succeeded but just for a moment – Sharadvan lost his senses for a moment but he immediately gained control. But in that second he dropped his semen. When wisdom dawned, he left behind his bow and arrow and went deep into the forest to do penance.
The ejected semen had fallen on an arrow nearby. It broke into two giving birth to a male and female child.
King Shantanu (the great grandfather of Pandavas and Kaurvas and father of Bhishma) who was passing by saw the children and he brought them to Hastinapura. As the king felt Kripa (pity) for the children, they were named Kripa and Kripi.
Kripi later married Dronacharya, the teacher of Kauravas and Pandavas.