Ibn Ezra on Numbers 26:11

ובני קרח לא מתו. והעד שמואל ובניו ובני בניו שהם המשוררים והם הנקראים הקרחים לבני קרח מזמור גם בתורה כתיב משפחת הקרחי והזכיר הכתוב ובני קרח עם בני ראובן בעבור כי בני דתן ואבירם גדולים וקטנים מתו והנה רעת דתן ואבירם קשה מרעת קרח: NOTWITHSTANDING THE SONS OF KORAH DIED NOT. Samuel,¹⁸The prophet Samuel. his sons, and his grandsons who were singers¹⁹In the temple. and were called the Korahites²⁰See I Chron. 6:18-23. is proof of this.²¹That Korah’s children did not die. The Book of Psalms states, For the leader; a Psalm of the sons of Korah (Ps. 49:1). The Torah also records the family of the Korahites (v. 58). Scripture mentions the sons of Korah with the sons of Reuben because the adult and the minor sons of Dathan and Abiram died. The wickedness of Dathan and Abiram was thus greater than the wickedness of Korah.²²Hence their children died. When Moses asked Dathan and Abiram to come to him, they refused and insulted Moses. We do not find the same with Korah (Num. 16:12-14).