[Pelefaifs]

A Doctor's Son has the advantage of becoming Doctor, but it is not without his own efforts to become one. The person who is born in a family where the living style, food etc. is more sattvic has the advantage of growing more with Satva guna and facilitated to learn more knowledge leading to Brahman.
A person who is born in a family totally ignorant of self-knowledge (or Brahman) does not enjoy this advantage. But everyone has the opportunity to attain oneness with Brahman in the way he progress towards it.
I felt it an achievement to climb by foot, the Tirumala shrine. But there are very simple people who does not know much about the concepts of Atman or Brahman, but they do it easily climbing the steps and they apply Turmeric and vermillion marks at every footstep while climbing. Here comes the difference between using your knowledge and using your physical ability to attain Brahman. The Lord is so kind to both of these Bhaktas who try to attain him by Knowledge or other simple ways.
Those who have the advantage of getting birth in Satvic families, but deviate from it and go the Tamas or Rajas way are choosing to go away from Brahman and they will get into more birth cycles than the others.