Bhagavad Gita · 1.39

कुलक्षये प्रणश्यन्ति कुलधर्माः सनातनाः।धर्मे नष्टे कुलं कृत्स्नमधर्मोऽभिभवत्युत॥

kula-kṣhaye praṇaśhyanti kula-dharmāḥ sanātanāḥ dharme naṣhṭe kulaṁ kṛtsnam adharmo 'bhibhavaty uta

With the destruction of the family, the eternal family traditions are destroyed. When dharma is lost, unrighteousness overtakes the entire family.

— Bhagavad Gita 1.39

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)