The parties must feel free to communicate. Not just talk to the other person, but talk with the other, exchanging ideas. The relationship must have commitment. Each party needs to feel that the other is committed to them, that they will not leave just because something is said or done with which they disagree. They need to know the other person has their best interest in mind and will stay with them.
Time is needed.
Many times there will be open communication, there will be a commitment, but that commitment has not passed the test of time. In relationships where there is communication and a commitment that has passed the test of time, there is trust. This is the kind of trust a person can depend on. Trust is an essential part of family life. In both the marital and parental relationships, there must be trust.