Introduction
Jarasandha is the powerful king of Magadha and the father-in-law of Kamsa. He is the enemy of Krishna.
This article primarily follows the Mahabharata. Where a well-known detail comes from a Puranic or later source, the article identifies it.
Family
Birth
He was born in two halves to the two queens of King Brihadratha, and the Rakshasi Jara joined them, and so he was called Jarasandha, "joined by Jara".
Enemy of Krishna
After Krishna killed Kamsa, Jarasandha attacked Mathura many times. Krishna finally moved the Yadavas to Dwaraka. Jarasandha held many kings captive.
Death
Krishna, Bhima and Arjuna went to Magadha in disguise and challenged him. Bhima and Jarasandha wrestled for days. Krishna hinted, by splitting a twig, that Bhima should tear him apart. Bhima killed him. This allowed Yudhishthira to hold the Rajasuya.