A people known before Israel
The Kenites first appear in the list of peoples living in the land promised to Abraham's descendants (Genesis 15:19). Scripture does not give a full family tree or detailed origin story for them, so there is a limit to what can be said with certainty.
Their name sounds similar to Cain's name in English, but the Bible does not plainly identify the Kenites as Cain's descendants. It is better not to build a conclusion on the similarity of names alone.
The Kenites, and the Kenizzites, and the Kadmonites,
Connected with Moses' family
The Kenites are closely linked with Moses through his father-in-law's household. Judges calls Moses' father-in-law a Kenite and says his descendants travelled with Judah into the south of the land (Judges 1:16). Yet Exodus also describes Moses' father-in-law as the priest of Midian (Exodus 3:1).
That may mean the family had ties to both the Midianites and the Kenites, or that these labels described overlapping communities. The text does not stop to explain every detail. What it does show is a real relationship of welcome and co-operation between Moses' family and Israel.
And the children of the Kenite, Moses' father in law, went up out of the city of palm trees with the children of Judah into the wilderness of Judah, which lieth in the south of Arad; and they went and dwelt among the people.
Heber and Jael
One Kenite household features prominently in the days of Deborah. Heber the Kenite had separated from other Kenites and camped near Kedesh (Judges 4:11). His wife, Jael, gave Sisera shelter after Israel's battle with Jabin's army, then killed him when he was vulnerable (Judges 4:17, Judges 4:21).
Jael's actions are part of a hard and violent war story, not a general instruction for personal behaviour. In that particular moment, the book of Judges presents her as playing a decisive part in Israel's deliverance from oppression (Judges 4:23-24).
Then Jael Heber's wife took a nail of the tent, and took an hammer in her hand, and went softly unto him, and smote the nail into his temples, and fastened it into the ground: for he was fast asleep and weary. So he died.
Remembered for kindness
Generations later, Saul warned the Kenites to leave the Amalekites before he attacked them. He specifically remembered that they had shown kindness to the Israelites when Israel came out of Egypt (1 Samuel 15:6). That brief moment says a great deal. Israel was meant to distinguish between the Amalekites' hostility and the Kenites' earlier care.
Some Kenites seem to have settled among Judah, while a group associated with the Rechabites is called Kenite in a genealogy (1 Chronicles 2:55). The Bible's picture is not of one large kingdom but of clans and households who remained identifiable in Israel's story.
So, the Kenites matter because they show that Israel's history included more than conflict with surrounding peoples. Some outsiders became trusted neighbours, shared Israel's journey, and were remembered with gratitude.