According to the text, why is reliance on the Guru superior to reliance on family for spiritual attainment?

According to Chapter 45, worldly relationships are ultimately unreliable for achieving one's spiritual goal. While family members like a mother and father show affection, a son may be focused on inheritance, and a wife on her marital status, none of them are true companions in the spiritual pursuit. The text posits that upon final reflection, only one's own self remains. Therefore, devotion to the Guru is paramount because, unlike family, the Guru is the one who can truly help with the spiritual goal. The Guru is identified as the true Brahman, the eternal reality, in contrast to the transient nature of worldly connections.