Complex sentence: Another model, sometimes referred to as "intimate network", may include relationships of varying significance to the people involved, but people who practice it do not explicitly label relationships primary or secondary, and hierarchies may be fluid and vague or nonexistent.
Split into simpler sentences: Another model, sometimes referred to as "intimate network", may include relationships of varying significance to the people involved. People in intimate networks may or may not explicitly label relationships primary or secondary, and hierarchies may be fluid and vague or nonexistent.