SB 10.1.10
vraje vasan kim akaron
madhupuryam ca kesavah
bhrataram cavadhit kamsam
matur addhatad-arhanam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Lord Krsna lived both in Vrndavana and in Mathura. What did He do there? Why did He kill Kamsa, His mother’s brother? Such killing is not at all sanctioned in the sastras.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One’s maternal uncle, the brother of one’s mother, is on the level of one’s father. When a maternal uncle has no son, his nephew legally inherits his property. Therefore, why did Krsna directly kill Kamsa, the brother of His mother? Maharaja Pariksit was very much inquisitive about the facts in this regard.