Board Thread:Episode Discussion/@comment-30505072-20180118160922/@comment-4241330-20180223003702

My theory is that Shenzi, Banzai and Ed discovered Janja, Cheezi, and Chungu as abandoned pups while fleeing Pride Rock. Then they went to the Outlands to raise them, only to be chased away by Scar's pride, thus leaving Janja and his potential crew to fend for themselves.

It's entirely possible the original trio survived the Pride Rock fire. They were even planned to appear in TLK2 as Zira's minions before the hyenas were replaced by lions.