Krishna is Lord Vishnu's avatar on earth. Radha was Mother Lakshmi's avatar in Vrindavan, where Krishna grew up. Therefore, Radha (Lakshmi) was Krishna's (Vishnu's) lover. After Krishna left Vrindavan to become the king of Mathura, Radha drowned Herself in the Yamuna. Later, She was reborn as Rukmini and married Krishna in Mathura.
- Hari Om 15th Nov 2011
When Krishna was married to Rukhmani, then why did he get involve with Radha?