Whatever intimacy develops between the human beings involved is secondary. The relationship is grounded in the Bible. The Word of God is the tool the Holy Spirit has provided for our spiritual direction. Discipleship involves more than just giving and getting good advice. Good advice is always helpful, but it is not discipleship.
Discipleship applies biblical principles to the decisions and difficulties of daily life.
The relationship is not exclusive. One of the characteristics of cults and many other false religions is that spiritual authority is located in a single human being. That is not how the church operates. Not every Christian needs to be in a special discipling relationship. God intends for us to grow through a variety of friendships.