Ugrasena’s brother was Devaka, his daughter was Devaki. She married Vasudeva. Devaki and Vasudeva were the parents of Krishna.
Kamsa heard a voice telling him that the eighth child of the couple would kill him. He did not trust and demanded that all of their children be killed.
Devaki was the reborn Aditi, cursed by Ditit to lose seven of her childen. The seventh she lost, but it was not killed.
See also Kashyapa
The story is included in the one of the appearance of Krishna