Mental Factor which Unites Other Factors
Your questions sounds somewhat similar to Visākha's question to the nun Dhammadinnā in MN44:


  “But ma’am, is that grasping the exact same thing as the five grasping aggregates? Or is grasping one thing and the five grasping aggregates another?”
  
  “That grasping is not the exact same thing as the five grasping aggregates. Nor is grasping one thing and the five grasping aggregates another. The desire and greed for the five grasping aggregates is the grasping there.”


In summary, desire and greed perpetuate the five grasping aggregates as identity. The dissolution of identity (your "condition that causes them to separate") is another one of visakha's questions later on in the sutta:


  “But ma’am, how does identity view not come about?”
  
  “It’s when an educated noble disciple has seen the noble ones, and is skilled and trained in the teaching of the noble ones. They’ve seen good persons, and are skilled and trained in the teaching of the good persons. They don’t regard form as self, self as having form, form in self, or self in form. They don’t regard feeling … perception … choices … consciousness as self, self as having consciousness, consciousness in self, or self in consciousness. That’s how identity view does not come about.”