The entire content of this mail is from Swami Chidbhavananda's translation of The Bhagavad Gita, published by Ramakrishna Mission.
The Fate of the Imperfect Yogi 37-45
1 Gita Sloka every day - Chapter 6 - Dhyana Yoga - Sloka 42
Athava yoginam eva kule bhavati dhimatam I
Etat hi durlabha taram loke janma yat idrisham II sloka 42
अथवा योगिनं एव कुले भवति धीमतां ।
एतत् हि दुर्लभ तरं लोके जन्म यत् ईदृशं ।। श्लोक ४२
Or he is born in a family of wise yogis only; a birth like this is verily very difficult to obtain in this world.
Yoga continues to be practised birth after birth until perfection is reached. The environment of the parentage obtained for this purpose is necessarily congenial. Of the two types of favourable families, that of the wise yogi is superior to that of the pure and prosperous. The how of it is explained in the next sloka.